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Resource Manager Section Section 3.1 Properties of Matter P 1 session 1/2 block
Objectives 1. Identify the characteristics of a
substance.
Activities/Features Discovery Lab: Observing Chemical
Change, p. 55
2. Distinguish between physical and
Careers Using Chemistry: Science Writer,
chemical properties. 3. Differentiate among the physical states of matter.
Problem-Solving Lab: How is compressed
gas released? p. 60
Section 3.2
4. Define physical change and list several
ChemLab: Matter and Chemical Reactions,
Changes in Matter P 1 session 1/2 block
common physical changes. 5. Define chemical change and list several indications that a chemical change has taken place. 6. Apply the law of conservation of mass to chemical reactions.
pp. 78–79
7. Contrast mixtures and substances. 8. Classify mixtures as homogeneous
MiniLab: Separating Ink Dyes, p. 68
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p. 56
or heterogeneous. 9. List and describe several techniques
used to separate mixtures.
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10. Distinguish between elements and
Elements and Compounds P 2 sessions 1 block
compounds. 11. Describe the organization of elements on the periodic table. 12. Explain how all compounds obey the laws of definite and multiple proportions.
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History Connection, p. 75 Chemistry and Society: Green Buildings,
p. 80
CHAPTER 3 RESOURCE MANAGER
National Science Content Standards UCP.1, UCP.2, UCP.3; A.1; B.2, B.3, B.4, B.5, B.6;G.1
State/Local Standards 1(A), 2(A), 2(D), 3(D), 4(A), 4(B), 4(C), 5(A)
Reproducible Masters Study Guide for Content Mastery, pp. 13–14 L2 Laboratory Manual, pp. 17–20 L2 Small-Scale Laboratory Manual, pp. 5–8 L2
Transparencies Section Focus Transparency 9 L1 ELL Teaching Transparency 7 L2 ELL P P
UCP.1, UCP.2, UCP.3; B.2, B.3, B.5, B.6
UCP.1, UCP.2, UCP.3; A.1; B.2; E.1
2(C), 4(B), 5(A), 5(C)
1(A), 4(C)
P for Content Mastery, Study Guide p. 15 L2 P MiniLab ChemLab and Worksheets, pp. 10 –12 L2 LS ChallengeP Problems, p. 3 L3 Laboratory Manual, LS pp. 21–24 L2 P LS
Study Guide for Content Mastery, P p. 16 L2 P ChemLab and MiniLab LS Worksheets, p. 9 L2 Forensics Laboratory Manual, P LS LS pp. 1–12 L2 Small-Scale Laboratory Manual, pp. 9–12 P L2
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UCP.1, UCP.2, UCP.3; A.1; B.1, B.2, B.3, B.6; E.2; F.4, F.6; G.1, G.2, G.3
1(A), 2(A), 2(B), 2(C), 2(D), 2(E), 3(B), 3(C), 3(E), 4(A), 4(B), 4(C), 4(D), 5(A), 6(C), 11(A)
Section Focus LS Transparency 10 L1 ELL P P Teaching LS Transparency 8 L2 ELL Math Skills P Transparency 2 LS L2 ELL
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Section Focus Transparency 12 L1 ELL Teaching Transparencies 9, LS 10 L2 ELL Math Skills P Transparency 3 L2 ELL P
LSP Key to National Science Content Standards: UCP Unifying Concepts and P Processes, A Science as Inquiry, B Physical Science, C Life Science, D Earth and Space Sciences, E Science and Technology, LS F Science in Personal and Social Perspectives, G History and Nature of Science Refer to pages 4T–5T of the Teacher Guide for an explanation of the National Science Content Standards correlations.
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Matter—Properties and Changes
Resource Manager Materials List ChemLab (pages 78–79) copper wire, AgNO3 solution, sandpaper, stirring rod, 50-mL graduated cylinder, 50-mL beaker, funnel, filter paper, 250-mL Erlenmeyer flask, ring stand, small iron ring, petri dish, paper clip, Bunsen burner, tongs
Discovery Lab (page 55) test tube, test-tube rack, 3M hydrochloric acid (10 mL), zinc metal, wood splint, burner
MiniLab (page 68) 9-oz. plastic cup (2), filter paper (2), scissors, water-soluble black felt marker, large nail, water
Demonstration (pages 62–63) piece of zinc (2 g), NaOH (5 g), porcelain evaporating dish, forceps, paper towel, hot plate, new pennies (3), water
Preparation of Solutions For a review of solution preparation, see page 46T of the Teacher Guide. Quantities are for a class of 30 students. ChemLab (pages 78–79)
1M silver nitrate (AgNO3) Dissolve 170 g AgNO3 in 600 mL distilled water. Make up to 1 L final volume with distilled water. CAUTION: Silver nitrate is toxic and harmful to skin and clothing. Discovery Lab (page 55)
3M hydrochloric acid Add 100 mL concentrated (12M) hydrochloric acid to 300 mL distilled water while stirring. CAUTION: Do NOT add the water to the acid.
54C
Assessment Resources
Additional Resources
Chapter Assessment, pp. 13–18 MindJogger Videoquizzes Alternate Assessment in the Science Classroom TestCheck Software Solutions Manual, Chapter 3 Supplemental Problems, Chapter 3 Performance Assessment in the Science Classroom Chemistry Interactive CD-ROM, Chapter 3 quiz
Spanish Resources ELL Guided Reading Audio Program, Chapter 3 ELL Cooperative Learning in the Science Classroom Lab and Safety SkillsP in the Science Classroom P Lesson Plans Block Scheduling Lesson Plans Texas Lesson Plans LS Texas Block Scheduling Lesson Plans LS
CHAPTER 3 RESOURCE MANAGER
Glencoe Technology The following multimedia for this chapter are available from Glencoe. VIDEOTAPE/DVD
CD-ROM
MindJogger Videoquizzes, Chapter 3
Chemistry: Matter and Change Separating Substances, Exploration Physical and Chemical Properties, Video Separating Mixtures, Exploration Metal Alloys, Experiment
VIDEODISC Cosmic Chemistry Elements, Still Periodic Table, Still Electrolysis of Water, Movie Sodium Chloride, Movie
Multiple Learning Styles Look for the following icons for strategies that emphasize different learning modalities. Kinesthetic Interpersonal Meeting Individual Needs, pp. 58, 61, 66; Reteach, Reteach, p. 69; Reinforcement, p. 72 p. 59; Check for Understanding, p. 69; Extension, p. 77 Intrapersonal Visual-Spatial Extension, pp. 59, 72; Chemistry Journal, p. 71; Check for Understanding, pp. 58, 65, 76; Enrichment, p. 74 Chemistry Journal, pp. 67, 76; Meeting Individual Linguistic Needs, p. 70; Visual Learning, p. 73; Reteach, p. 77 Chemistry Journal, pp. 56, 64; Portfolio, p. 57
Key to Teaching Strategies L1 Level 1 activities should be appropriate for students with learning difficulties. L2 Level 2 activities should be within the ability range of all students. L3 Level 3 activities are designed for above-average students. ELL ELL activities should be within the ability range of English Language Learners. COOP LEARN Cooperative Learning activities are designed P small group work. for P P P These strategies represent student products that can be P placed into a best-work portfolio.
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Assessment Planner Portfolio Assessment Problem-Solving Lab, TWE p. 60 Assessment, TWE, p. 66 ChemLab, TWE, p. 79 Portfolio, TWE, p. 81 Performance Assessment Assessment, TWE, pp. 58, 62 Discovery Lab, SE, p. 55 MiniLab, SE, p. 68 ChemLab, SE, pp. 78–79
Knowledge Assessment Assessment, TWE, pp. 59, 65 Demonstration, TWE, p. 63 Section Assessment, SE, pp. 60, 65, 69, 77 Chapter Assessment, SE, pp. 82–85 Skill Assessment MiniLab, TWE, p. 68 Assessment, TWE, pp. 69, 73, 77
These strategies are useful in a block scheduling format.
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Tying to Previous Knowledge Have students review the following concepts before studying this chapter. Chapter 1: matter, qualitative and quantitative aspects of chemistry Chapter 2: significant figures
Matter—Properties and Changes What You’ll Learn ▲
Using the Photo
▲ ▲
evident in the coral reef (mostly calcium carbonate); the divers’ bodies (compounds of carbon, hydrogen, oxygen, nitrogen, phosphorus, calcium, sulfur, and trace amounts of other metals); the divers’ wet suits made of molecules of the hydrocarbon rubber; the metal of the scuba tanks. Liquids are most evident in the solution of salt water. Gases are evident in the escaping oxygen bubbles.
▲
Ask students to identify the types of matter seen in this photograph. Encourage them to be specific in their descriptions. Solids are
3
You will distinguish between physical and chemical properties. You will classify matter by composition: element, compound, or mixture. You will identify observable characteristics of chemical reactions. You will explain the fundamental law of conservation of mass.
Why It’s Important You are completely surrounded by matter. To better understand this matter—how it affects you, how you affect it, and how it can be manipulated for the benefit of society—you need to build a basic understanding of the types and properties of matter.
Chapter Themes The following themes from the National Science Education Standards are covered in this chapter. Refer to page 4T of the Teacher Guide for an explanation of the correlations. Systems, order, and organization (UCP.1) Evidence, models, and explanation (UCP.2) Form and function (UCP.5)
Visit the Chemistry Web site at science.glencoe.com to find links about matter.
Chemistry is the study of matter and its properties. Every aspect of these divers’ environment, under water and on land, is some form of matter.
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Chapter 3
DISCOVERY LAB P Purpose
Teaching Strategies
Students will examine several types of chemical changes.
• If you are using smaller test tubes, about 3 to 5 mL of 6M HCl will work. • See page 54C for preparation of solutions.
lighted splint is brought close to the mouth of the test tube, the hydrogen gas reacts with oxygen in the air to produce gaseous water. The reaction produces a pop or “bark.”
Expected Results
Analysis
The zinc reacts with hydrochloric acid to produce zinc chloride (which is soluble and, therefore, not easily seen) and hydrogen gas (seen as bubbles). When a
Answers will vary. Students might have thought that no reaction would occur. The “bark” is the result of a reaction between the gas that was produced and oxygen.
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Safety and Disposal Use gloves when handling HCl. The HCl can be washed down the sink with a lot of water. The unreacted zinc can be reused. ZnCl2 solution can be flushed down the drain.
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Section 3.1
DISCOVERY LAB Observing Chemical Change
1 Focus
onsider the metal objects that are part of the everyday world. A mailbox, for example, stands outside day in and day out, without seeming to change. Under what conditions does metal exhibit chemical change?
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Focus Transparency Before presenting the lesson, display Section Focus Transparency 9 on the overhead projector. Have students answer the accompanying questions using Section Focus Transparency Master 9. L1
Safety Precautions Always wear eye goggles, gloves, and an apron when experimenting with chemicals. Use caution when handling an open flame.
Procedure Materials
1. Place a piece of zinc metal in a large test tube.
large test tube test-tube holder or rack 10 mL HCl zinc metal wood splint match or burner
2. Add approximately 10 mL of 3M hydrochloric acid (HCl) to the test
ELL
tube. Record your observations. CAUTION: HCI causes burns and hazardous fumes. 3. When the zinc and HCl have reacted for approximately 1 min,
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bring a lighted, glowing wood splint to the mouth of the test tube. CAUTION: Be sure the test tube is facing away from your face when the splint is brought near. Again record your observations.
Section Focus
Transpare ncy
9
States of Matter Use with
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Analysis
Chapter 3, Sectio n 3.1
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What may have caused the dynamic reaction you observed in step 3? Did you expect this reaction? Explain.
Properties of Matter
© Glencoe/Mc Graw-Hill, a division of the McGr
3.1
Copyright
Section
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Inc.
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Objectives • Identify the characteristics of a substance. • Distinguish between physical and chemical properties. • Differentiate among the physical states of matter.
Vocabulary substance physical property extensive property intensive property chemical property states of matter solid liquid gas vapor
Imagine yourself scuba diving through a complex biological ecosystem such as a coral reef. What kinds of things fill your imagination? Regardless of what you envision, there is only one answer—you see matter. The diversity of matter in the world and in the universe is astounding. From pepperoni pizzas to supernovas, it’s all matter. If we are to understand this diversity, we must start with a way of organizing and describing matter.
Substances Recall from Chapter 1 that chemistry is the study of matter, and matter is anything that has mass and takes up space. Everything around you is matter; including things such as air and microbes, which you cannot see. For example, table salt is a simple type of matter that you are probably familiar with. Table salt has a unique and unchanging chemical composition. It is always 100% sodium chloride and its composition does not change from one sample to another. Matter that has a uniform and unchanging composition is called a substance, also known as a pure substance. Table salt is a substance. Another example of a pure substance is water. Water is always composed of hydrogen and oxygen. Seawater, on the other hand, is not a substance because samples taken from different locations will probably have 3.1 Properties of Matter
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Resource Manager Study Guide for Content Mastery, pp. 13–14 L2 Solving Problems: A Chemistry Handbook, Section 3.1 L2 Section Focus Transparency 9 and Master L1 ELL Lab Manual, pp. 17–20 L2 P
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What ma tter is sh own in all three ph What is otograp differen hs? t about the matte r in each photograp Chemistry: h? Matter and 2
Change
Section Focus Tran sparencies
2 Teach Quick Demo Show students a beaker of distilled water and a beaker of unsaturated salt solution. Ask them if the beakers contain pure substances and how they would confirm their hypothesis. A visual inspection
would lead students to believe both were pure substances. However, some students may realize that further tests would be necessary to confirm this. Students may suggest evaporation or the use of a conductivity apparatus to show that the second beaker P is actually a mixture of substances. It is a solution.
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Identifying Misconceptions Students may think that because extensive and intensive properties are both physical properties that they both depend on the amount of the substance being investigated. Uncover the Misconception Review the definitions of extensive and intensive properties. Present the students with a table or chart from some authoritative source such as the CRC Handbook of Chemistry and Physics to reinforce the idea that the concept of extensive and intensive properties is a valid distinction. Demonstrate the Concept Show the students two pieces of the same type of wood that are obviously different lengths. Measure each piece and explain that length is an extensive physical property because the measurements are different for the different amount of wood present. Next place the two pieces of wood in a container of water and show how both float. In this case, density is the intensive property that is illustrated. Explain how you have proven that density of the wood is the same for the long piece as for the short piece because both pieces float the same regardless of the amount of wood in the water. Assess New Knowledge Have the students research physical properties of some common substances and create a table listing some extensive and some intensive properties. Ask the students to choose one property of a substance they investigated and explain why that property is extensive or intensive. Have them P offer some demonstration to illustrate the concept.
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Pages 54–57 1(A), 2(A), 3(D), 4(A), 4(C)
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Science Writer Do you get excited about news in science and technology? Do you like to explain information in a way that others find interesting and understandable? Then consider a career as a science writer. Science writers keep up-to-date on what is happening in the world of science and translate that news so nonscientists can understand it. These writers work for newspapers, magazines, scientific publications, television stations, and Internet news services. Lots of curiosity, as well as a degree in a science and/or journalism, is essential.
differing compositions. That is, they will contain differing amounts of water, salts, and other dissolved substances. Given this definition, what other pure substances are you familiar with? Substances are important; much of your chemistry course will be focused on the processes by which substances are changed into different substances.
Physical Properties of Matter You are used to identifying objects by their properties—their characteristics and behavior. For example, you can easily identify a pencil in your backpack because you recognize its shape, color, weight, or some other property. These characteristics are all physical properties of the pencil. A physical property is a characteristic that can be observed or measured without changing the sample’s composition. Physical properties describe pure substances, too. Because substances have uniform and unchanging compositions, they have consistent and unchanging physical properties as well. Density, color, odor, taste, hardness, melting point, and boiling point are common physical properties that scientists record as identifying characteristics of a substance. Sodium chloride forms solid, white crystals at room temperature, all having the same unique salty taste. Table 3-1 lists several common substances and their physical properties. Table 3-1 Physical Properties of Common Substances Substance Oxygen Mercury
Miners relied on the physical property of density to distinguish gold (19 g/cm3) from the worthless minerals in their sluice pans. The density of pyrite, a worthless mineral often mistaken for gold, is 5 g/cm3.
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State at 25°C
Melting point (°C)
Boiling point (°C)
Density (g/cm3)
Colorless
Gas
⫺218
–183
0.0014
Silver
Liquid
–39
357
13.5
Colorless
Liquid
0
100
1.00
Sucrose
White
Solid
185
Decomposes
1.59
Sodium chloride
White
Solid
801
1413
2.17
Water
Figure 3-1
Color
Extensive and intensive properties Physical properties can be further described as being one of two types. Extensive properties are dependent upon the amount of substance present. For example, mass, which depends on the amount of substance there is, is an extensive property. Length and volume are also extensive properties. Density, on the other hand, is an example of an intensive property of matter. Intensive properties are independent of the amount of substance present. For example, density of a substance (at constant temperature and pressure) is the same no matter how much substance is present. A substance can often be identified by its intensive properties. In some cases, a single intensive property is unique enough for identification. During the California gold rush, miners relied on gold’s characteristic density (19 g/cm3) to separate valuable gold-containing flakes from riverbed sand. The process used by the miners is shown in Figure 3-1. Another intensive property of gold is its distinctive appearance. Unfortunately, miners often learned that identification of gold based on appearance alone was misleading. Figure 3-2 shows a nugget of the relatively worthless
Chapter 3 Matter—Properties and Changes
CHEMISTRY JOURNAL Life on Other Planets Linguistic Ask students to write a creative story about noncarbonbased life on another planet. As they research the elements that make up the life forms of their planet, they should identify whether the properties are physical or chemical. If the properties P are physical, students should identify them as either extensive or intensive. L2
CD-ROM Chemistry: Matter and Change Exploration: Separating Substances Video: Physical and Chemical Properties
Figure 3-2 Gold a and pyrite, or "fool’s gold" b , have similar physical properties but are different samples of matter.
a Gold
b Pyrite
mineral pyrite, often called “fool’s gold,” which looks very similar to actual gold nuggets. Such errors in identification based on the intensive property of appearance fooled many miners into falsely thinking they had struck it rich!
Chemical Properties of Matter Some properties of a substance are not obvious unless the substance has changed composition as a result of its contact with other substances or the application of thermal or electrical energy. The ability of a substance to combine with or change into one or more other substances is called a chemical property. The ability of iron to form rust when combined with air is an example of a chemical property of iron. Similarly, the inability of a substance to change into another substance is also a chemical property. For example, when iron is placed in nitrogen gas at room temperature, no chemical change occurs. The fact that iron does not undergo a change in the presence of nitrogen is another chemical property of iron.
Figure 3-3 These photos illustrate some of the physical and chemical properties of copper as it exists in the form of hardware a and the Statue of Liberty b .
CAREERS USING CHEMISTRY Career Path A career
as a science writer would include high school courses in Earth science, math, chemistry, biology, and physics. College course work should build on the science foundation and also include technical writing and journalism. Career Issue Have the students read science articles on various topics and in a variety of mainstream publications. Ask them to evaluate the effectiveness of the writing. How well did the writer clarify or explain a scientific concept or development?
Every substance has its own unique set of physical and chemical properties. Table 3-2 lists several of these properties of copper. Figure 3-3 shows physical and chemical properties of copper. What physical and chemical properties are evident in these photos? a Table 3-2 Properties of Copper
• Reddish brown, shiny • Easily shaped into sheets (malleable) and drawn into wires (ductile) • Good conductor of heat and electricity • Density ⫽ 8.92 g/cm3
Chemical properties • Forms green copper carbonate compound when in contact with moist air • Forms new substances when combined with nitric acid and sulfuric acid • Forms a deep blue solution when in contact with ammonia
For More Information
• Melting point ⫽ 1085°C • Boiling point ⫽ 2570°C
For more information about careers in science writing, students can contact the
b
3.1 Properties of Matter
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Portfolio Portfolio
National Association for Science Writers, Inc. P.O. Box 294 Greenlawn, NY 11740 www.nasw.org
In-Text Question
Properties and Uses Linguistic Have students use the CRC Handbook of Chemistry and Physics to research the physical and chemical properties of a particular element or compound. Next, have them write a summary relating
Show students some copper turnings or foil and have them list the observable properties of these items. Roll the copper into a ball small enough to fit into a crucible. Determine the mass of the crucible with the copper in it. Next, heat the copper strongly for 5 to 10 minutes and have students make observations again. Ask them to predict what has happened to the mass, then weigh the copper oxide product. (When finished, CuO can be thrown away.) Ask students to distinguish between P physical and chemical properties that they have witnessed.
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Observing Properties of Matter
Physical properties
Quick Demo
how that particular property is useful for a product made with that element or compound. For example, copper’s malleability, P conductivity, and high melting point might make it ideal for cookware. L2 P
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Page 57 What physical and chemical properties are evident in these photos? Physical: color, luster, hardness, malleability, ductility, physical state Chemical: formation of green copper carbonate
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Observations of properties may vary depending on the conditions of the immediate environment. It is important to state the specific conditions in which observations are made because both chemical and physical properties depend on temperature and pressure. Consider the properties of water, for example. You may think of water as a liquid (physical property) that is not particularly chemically reactive (chemical property). You may also know that water has a density of 1.00 g/cm3 (physical property). These properties, however, apply only to water at standard “room” temperature and pressure. At temperatures greater than 100°C, water is a gas (physical property) with a density of about 0.0006 g/cm3 (physical property) that reacts rapidly with many different substances (chemical property). As you can see, the properties of water are dramatically different under different conditions.
Assessment Performance Give students a large (3 to 4 cm diameter) cork and ask them to design an experiment to determine its density. Next, have them run the cork through a cork press (or a vice) and ask them to reassess density. Ask them to explain the results of their experiment in terms of the packing arrangement of the atoms. Students will see that pressing the cells together increases the number of atoms per unit volume; hence, the density increases. Use the
States of Matter Go to the Chemistry Interactive CD-ROM to find additional resources for this chapter.
Performance Task Assessment List for Designing an Experiment in PASC, p. 23.
Solids A solid is a form of matter that has its own definite shape and volume. Wood, iron, paper, and sugar are examples of solids. The particles of matter in a solid are very tightly packed; when heated, a solid expands, but only slightly. Because its shape is definite, a solid may not conform to the shape of the container in which it is placed. The tight packing of particles in a solid makes it incompressible; that is, it cannot be pressed into a smaller volume. It is important to understand that a solid is not defined by its rigidity or hardness; the marble statue in Figure 3-4 is rigid whereas wax sculpture is soft, yet both are solids.
3 Assess Check for Understanding VisualSpatial Fill a 50 mL graduated
cylinder with 25 mL of water. Fill another graduated cylinder with 25 mL of alcohol (methyl, ethyl, or isopropyl may be used). Ask the students to predict what will occur when the alcohol is poured into the 50 mL cylinder containing the water and mixed. Students will typically think the volumes will add to a full 50 mL of alcohol–water mixture; however, the volume is not additive. Molecules of alcohol slip in between the molecules of water. Reinforce this by filling a beaker to the top with marbles and asking students if more material can be added. Then add sand or water to demonstrate. To P dispose of alcohols, evaporate under a hood.
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Imagine you are sitting on a bench, breathing heavily and drinking water after a tiring game of soccer. In this scenario, you are in contact with three different forms of matter; the bench is a solid, the water is a liquid, and the air you breathe is a gas. In fact, all matter that exists on Earth can be classified as one of these physical forms called states of matter. Scientists recognize a fourth state of matter called plasma, but it does not occur naturally on Earth except in the form of lightning bolts. The physical state of a substance is a physical property of that substance. Each of the three common states of matter can be distinguished by the way it fills a container.
Liquids A liquid is a form of matter that flows, has constant volume, and takes the shape of its container. Common examples of liquids include water, blood, and mercury. The particles in a liquid are not rigidly held in place and are less closely packed than are the particles in a solid: liquid particles
Figure 3-4 The properties of the solid materials marble a and wax b make these sculptures possible. Particles in a solid are tightly packed c , giving definite shape and volume to the solid.
Solid c
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Chapter 3 Matter—Properties and Changes
M EETING I NDIVIDUAL N EEDS
Resource Manager
Learning Disabled
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Kinesthetic Pass out three plastic petri dishes and a collection of marbles or large gauge metal shot. Have the students arrange the marbles or shot in the dishes to show the relative packing arrangement of solids, liquids, and gases. These can also be displayed on the overP head projector to show atomic motion in the three states of matter. L1 ELL
Teaching Transparency 7 and Master L2 ELL
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Figure 3-5 a Despite having different shapes, each of these measuring cups holds the same volume of liquid. b River water flows to fit within the boundaries of its banks, regardless of the curves along its path. c Molecules in a liquid are closely packed but can still move relatively freely.
Liquid a
c
b
Reteach Kinesthetic Have students
act out the packing of the different states of matter by “becoming” atoms themselves. Isolate a particular area of the classroom as the stage so that students can visualize the relative packing of atoms in the different states. L1 ELL
Extension are able to move past each other. This allows a liquid to flow and take the shape of its container, although it may not completely fill the container. A liquid’s volume is constant: regardless of the size and shape of the container in which the liquid is held, the volume of the liquid remains the same. This is why measuring cups used in cooking, such as those pictured in Figure 3-5, can be made in a variety of shapes yet still measure the same volume. Because of the way the particles of a liquid are packed, liquids are virtually incompressible. Like solids, liquids tend to expand when heated. Gases A gas is a form of matter that flows to conform to the shape of its container and fills the entire volume of its container. Examples of gases include neon, which is used in the lighted artwork in Figure 3-6; methane, which is used in cooking; and air, which is a mixture of gases. Compared to solids and liquids, the particles of gases are very far apart. Because of the significant amount of space between particles, gases are easily compressed. The problem-solving LAB in this section poses several important questions about the practical use of compressed gas. It is likely that you are familiar with the word vapor as it relates to the word gas. The words gas and vapor, while similar, do not mean the same thing and should not be used interchangeably. The word gas refers to a substance that is naturally in the gaseous state at room temperature. The word vapor refers to the gaseous state of a substance that is a solid or a liquid at room temperature. For example, steam is a vapor because at room temperature water exists as a liquid.
a
Gas
P Intrapersonal Have students
search the Internet for examples of new materials being developed by various chemical LS (DuPont, Dow, manufacturers Kodak, for instance). Ask students P to relate the properties of the new materials to the arrangement of the atoms or molecules as solids, liquids,LS or gases.
Assessment Knowledge Ask students
to decide whether the following statements are true or false, and to support their choice with text references. • A vapor and a gas are the same thing. F • A liquid conforms to its container. T • Particles of a gas are spaced closer together than particles of a liquid. F • A solid has definite shape but changeable volume. F
Figure 3-6 a Molecules in a gas are far apart and freely moving. b Neon gas completely fills the tubes of the electric artwork.
b
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Internet Address Book Note Internet addresses that you find useful in the space below for quick reference.
Pages 58–59 4(A), 4(B), 5(A)
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problem-solving LAB P Purpose
Students will deduce the method by which the flow of gas out of a LS compressed tank is controlled.
problem-solving LAB How is compressed gas released? Recognizing Cause and Effect Tanks of com-
Teaching Strategies
pressed gases are a common sight in a chemistry laboratory. For example, nitrogen is often flowed over a reaction in progress to displace other gases that might interfere with the experiment. Given what you know about the properties of gases, explain how compressed nitrogen is released.
• Identify several real-world situa-
Analysis
tions (outside a laboratory) where compressed gases are used. • Identify control and safety features in these situations.
By definition, the particles of gases are far apart and gases tend to fill their container, even if the container is a laboratory room. Tanks of compressed gas come from the supplier capped to prevent the gas from escaping. In the lab a chemist or technician attaches a regulator to the tank and secures the tank to a stable fixture.
Process Skills
Inferring, predicting, thinking critically, recognizing cause and effect
Thinking Critically
1. Some kind of valve must be attached that can limit the exit orifice, thereby limiting the amount of gas that is released. 2. Without the regulator device, the gas would rush out of the tank with a force powerful enough to transform it into a dangerous, uncontrolled projectile.
Section
3.1
be controlled for practical use. 2. Predict what would happen if the valve on a
full tank of compressed gas were suddenly opened all the way or if the full tank were punctured.
Assessment
1.
Describe the characteristics that identify a sample of matter as being a substance.
2.
Classify each of the following as a physical or chemical property. a. b.
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c. d. e.
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1. Explain why the flow of compressed gas must
The fact that substances can change form, as in the example of water changing to steam, is another important concept in chemistry. If you review what you just learned about physical properties of substances, you can see that because the particular form of a substance is a physical property, changing the form introduces or adds another physical property to its list of characteristics. In fact, resources that provide tables of physical and chemical properties of substances, such as the CRC Handbook of Chemistry and Physics, generally include the physical properties of substances in all of the states in which they can exist.
Assessment Portfolio Have students research the breathing apparatus that a scuba diver uses and compare that equipment with compressed gas equipment in a laboratory. Reports can be placed in students’ portfolios. L2 P
Thinking Critically
3.
Iron and oxygen form rust. Iron is more dense than aluminum. Magnesium burns brightly when ignited. Oil and water do not mix. Mercury melts at ⫺39°C.
4.
Thinking Critically Using what you know about the compressibility of gases, explain why the oxygen in a SCUBA tank is compressed.
5.
Interpreting Data Bromine is a reddish-brown liquid that boils at 59°C. Bromine is highly reactive with many metals. For example, it reacts with sodium to form a white solid. Classify each of these properties of bromine as either a physical or a chemical property.
Create a table that describes the three common states of matter in terms of their shape, volume, and compressibility.
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Pages 60–61 2(D), 4(A), 4(B), 5(A)
Section 3.1
Assessment
1. The sample of matter must have a uniform and unchanging composition to be a substance. 2. a. chemical d. physical b. physical e. physical c. chemical
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Chapter 3 Matter—Properties and Changes
3. Table should list solid (definite volume, definite shape, incompressible); liquid (definite volume, fills container shape, virtually incompressible); gas (fills volume of container, takes shape of container, compressible).
4. Particles in a gas are spaced far apart and are easily compressed. Therefore, it is possible to put a significant volume of oxygen in a tank, which allows the diver to remain under water longer. 5. color, physical; boiling point, physical; reactive with metals, chemical
Changes in Matter
Section 3.2
You learned in Section 3.1 that scientists can describe matter in terms of physical and chemical properties. For example, a physical property of copper allows it to be drawn into copper wire, and a chemical property of copper accounts for the fact that when a solution of copper ions is combined with ammonia, the copper solution changes to a deep blue color. The key concept in both of these examples is that the substance copper changed in some way. In this section, you’ll explore how matter changes as a result of its physical and chemical properties.
Objectives
Physical Changes
• Apply the law of conservation of mass to chemical reactions.
Focus Transparency
• Define chemical change and list several indications that a chemical change has taken place.
Before presenting the lesson, display Section Focus Transparency 10 on the overhead projector. Have students answer the accompanying questions using Section Focus Transparency Master 10. L1 ELL
Vocabulary physical change chemical change law of conservation of mass
P
Section Focus
Transpare ncy
10
Physical an Changes d Chemical Use with
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Chapter 3, Sectio n 3.2
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Figure 3-7
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Inc.
a Condensation on an icy beverage glass is the result of the phase change of water in a gaseous state to water in a liquid state. b The characteristic “fog” of dry ice is actually fine water droplets formed by condensation of water vapor from the air surrounding the very cold dry ice. Refer to Table C-1 in Appendix C for a key to atom color conventions.
aw-Hill Comp anies,
A substance often undergoes changes that result in a dramatically different appearance yet leave the composition of the substance unchanged. An example is the crumpling of a sheet of aluminum foil. While the foil goes from a smooth, flat, mirrorlike sheet to a round, compact ball, the actual composition of the foil is unchanged—it is still aluminum. Changes such as this, which alter a substance without changing its composition, are known as physical changes. Cutting a sheet of paper and breaking a crystal are other examples of physical changes in matter. Can you name some other physical changes? Your list might include verbs such as bend, grind, crumple, split, and crush, all of which indicate physical change. As with other physical properties, the state of matter depends on the temperature and pressure of the surroundings. As temperature and pressure change, most substances undergo a change from one state (or phase) to another. For example, at atmospheric pressure and at temperatures below 0°C, water is in its solid state, which is known as ice. As heat is added to the ice, it melts and becomes liquid water. This change of state is a physical change because even though ice and water have very different appearances, their composition is the same. If the temperature of the water increases to 100°C, the water begins to boil and liquid water is converted to steam. Melting and formation of a gas are both physical changes and phase changes. Figure 3-7 shows condensation, another common phase change. When you encounter terms such as boil, freeze, condense, vaporize, or melt in your study of chemistry, the meaning generally refers to a phase change in matter.
1 Focus
• Define physical change and list several common physical changes.
© Glencoe/Mc Graw-Hill, a division of the McGr
3.2
Copyright
Section
1 2
How is th e tree ch anged by each actio Which ac n shown? tion do you think shows a more co mplete ch ange?
Chemistry: Matter and Change
Section Focus Tran sparencies
2 Teach Quick Demo b
a
cb
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3.2 Changes in Matter
M EETING I NDIVIDUAL N EEDS
Resource Manager
Gifted Kinesthetic Have gifted students identify an unknown from a list of possibilities based on the melting point and boiling point. Students should plot a heating/cooling P graph of time on the x-axis versus temperature on the y-axis. L3
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Study Guide for Content Mastery, p.15 L2 Challenge Problems, p. 3 L3 Solving Problems: A Chemistry Handbook, Section 3.2 L2 Section Focus Transparency 10 and Master L1 ELL P
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CAUTION: Perform this demo under a hood. Place several moth balls in a beaker. Place a flask half filled with cold water on top to serve as a condensing “lid.” Heat the moth balls until they have melted and ask students to observe and diagram the changes. Remove the heat source and ask students to again observe the changes.
With heat, students will see the change from solid to liquid, solid to vapor, and liquid to vapor. On cooling, students will see liquid P to solid and vapor to solid, or vapor to a liquid.
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The temperature and pressure at which a substance undergoes a phase change are important physical properties. These properties are listed as the melting and boiling points of the substance. Table 3-1 on page 56 provides this information for several common substances. Like density, the melting point and boiling point are intensive physical properties that may be used to identify unknown substances. For example, if an unknown solid melts at 801°C and boils at 1413°C—very high temperatures—it is most probably sodium chloride, or common table salt. Tables of intensive properties, such as those given in the CRC Handbook of Chemistry and Physics, are indispensable tools in identifying unknown substances from experimental data.
Quick Demo Pour 20 to 25 mL of ethanol into an empty water cooler jug or plastic gallon milk bottle. Roll the ethanol around to coat the inside of the bottle and pour off the excess. Turn off the classroom lights and, with a lighted splint that is taped to a meter stick, ignite the top of the bottle. CAUTION: Perform from behind an explosion shield and keep your hand clear of the bottle opening. After the explosion, show the water that forms in the reaction by pouring it into a beaker. Students will frequently clamor for an encore performance, which is most often unsuccessful because of the presence of the other product of the reaction, carbon dioxide. Have the students identify the reactants (ethanol and oxygen) and the products
(water and carbon dioxide). The carbon dioxide canP be flushed out of the bottle by water displacement.
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Chemical Changes
Figure 3-8 a The formation of a gas or solid when reactants mix often indicates that a chemical reaction has taken place. Rust is the result of a chemical reaction. b Color changes generally indicate that a chemical reaction has taken place. One example is the color change of tree leaves in the fall.
As you learned earlier, chemical properties relate to the ability of a substance to combine with or change into one or more substances. A process that involves one or more substances changing into new substances is called a chemical change, which is commonly referred to as a chemical reaction. The new substances formed in the reaction have different compositions and different properties from the substances present before the reaction occurred. For example, the crushing of grapes that is part of the wine-making process is a physical change, but the fermentation of the juice, sugars, and other ingredients to wine is a chemical change. The Chemistry and Society feature at the end of the chapter describes some interesting consequences of physical and chemical changes in the production of concrete. Let’s consider again the rusting of iron. When a freshly exposed iron surface is left in contact with air, it slowly changes into a new substance, namely, the rust shown in Figure 3-8a. The iron reacts with oxygen in the air to form a new substance, rust. Rust is a chemical combination of iron and oxygen. In chemical reactions, the starting substances are called reactants and the new substances that are formed are called products. Thus iron and oxygen are reactants and rust is a product. When you encounter terms such as explode, rust, oxidize, corrode, tarnish, ferment, burn, or rot, the meaning generally refers to a chemical reaction in which reactant substances produce different product substances.
Assessment Performance The reaction of iron with oxygen costs American industry a great deal of money. Have the students choose a particular industry (such as agriculture, transportation, or construction) and give an oral report on how the industry deals with the problem of rust. Use the Performance Task Assessment List for Oral Presentation in PASC, p. 71. a
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Demonstration Atoms inPMotion
b
Chapter 3 Matter—Properties and Changes
(5 g); porcelain evaporating dish; forceps; paper towels; hot plate Safety Precautions
Purpose
To observe atomic motion and the formation of an alloy, brass
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Materials
New pennies (3); zinc (2 g); NaOH 62
Disposal Decant the cooled NaOH solution from the solid zinc. Neutralize the NaOH and rinse down the drain. Dry the zinc in an evaporating dish and reuse. Do not allow the zinc plating solution to come in contact with flammable materials.
Procedure
Dissolve 5 g NaOH in 25 mL of water in an evaporating dish. CAUTION: NaOH causes severe burns; avoid skin contact. Rinse spills with plenty of water. Wear goggles and apron. Add a 2 g piece of zinc to the NaOH solution. Place the solution on the hot plate and heat to just below the boiling point. Keep one penny as a control. Immerse two new pennies in the NaOH–zinc plating bath. After one minute,
Enrichment
a
b Figure 3-9
Evidence of a chemical reaction As Figure 3-8a shows, rust is a brownish-orange powdery substance that looks very different from iron and oxygen. Rust is not attracted to a magnet, whereas iron is. The observation that the product (rust) has different properties than the reactants (iron and oxygen) is evidence that a chemical reaction has taken place. A chemical reaction always produces a change in properties. Figures 3-8 and 3-9 illustrate several common indicators of chemical change. The CHEMLAB at the end of the chapter provides a practical laboratory experience with chemical reactions.
a Energy changes indicate chemical reactions. For example, the burning of wood is a common example of a reaction that releases heat. b The change in the smell of a substance or the production of an odor may be an indication of a chemical reaction.
Conservation of Mass Although chemical reactions have been observed over the course of human history, it was only in the late eighteenth century that scientists began to use quantitative tools to monitor chemical changes. The revolutionary quantitative tool developed at this time was the analytical balance, which was capable of measuring very small changes in mass. By carefully measuring mass before and after many chemical reactions, it was observed that, although chemical changes occurred, the total mass involved in the reaction remained constant. The constancy of mass in chemical reactions was observed so often that scientists assumed the phenomenon must be true for all reactions. They summarized this observation in a scientific law. The law of conservation of mass states that mass is neither created nor destroyed during a chemical reaction—it is conserved. This law was one of the great achievements of eighteenth-century science. The equation form of the law of conservation of mass is
Figure 3-10 The development of scientific tools such as this analytical balance gave a degree of precision to measurements that greatly improved general scientific understanding.
The first true chemist is considered by many to be Robert Boyle (1627–1691), known for his work on the relationship between gas pressure and volume. The German chemist Georg Stahl (1660–1734) was also interested in the chemistry and physics of gases, in particular, combustion. He believed that when a substance burned, “phlogiston” flowed out of the material. The English scientist and clergyman Joseph Priestley (1773–1804) is credited with the discovery of the active role of oxygen in combustion. He called oxygen “dephlogisticated air.” Antoine Lavoisier, with carefully recorded measurements, showed that mass was conserved in combustion reactions involving oxygen. It was Lavoisier who named the gas that supports combustion “oxygene,” meaning “generator of acid” (it was originally believed to be an important part of all acids). Have students research and report on one of these early pioneers. L2
CHEMLAB ChemLab 3, located at the end of the chapter, can be used at this point in thePlesson.
Massreactants ⫽ Massproducts The French scientist Antoine Lavoisier (1743–1794) was one of the first to use an analytical balance like the one shown in Figure 3-10 to monitor chemical reactions. He studied the thermal decomposition of mercury(II) oxide, known then as calx of mercury. Mercury(II) oxide is a powdery red solid. When it is heated, the red solid reacts to form silvery liquid mercury and colorless oxygen gas as shown in Figure 3-11 on the next page. The color change and production of a gas are indicators of a
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3.2 Changes in Matter
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Teaching Transparency 8 and Master L2 ELL Math Skills Transparency 2 and Master L2 ELL P
use forceps to turn the pennies over. Keep the pennies immersed until they are silver in color. Using forceps, remove the two coins from the hot bath, rinse with cold water, and pat dry with paper towels. Remove the evaporating dish from the hot plate. Place one of the plated pennies on the hot surface. In a few seconds, the plated coin will return to its original copper color. After a few more seconds, the color of the coin will appear golden. Remove the coin
from the hot plate and allow it to cool. CAUTION: Do not touch the hot penny. Display the three pennies to the class. Results
The control penny remains copper colored. The zinc-plated penny is silver colored. The third penny is gold colored. Analysis
Describe the alloy brass. Brass is a solid
solution of the metallic P elements copper and zinc. P
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Assessment P
LS students why Knowledge Ask heat is needed to cause LS the zinc coating to diffuse into the copper. Heat increases the motion of the atoms and separates and LS expands the layers of atoms, thus allowing them to migrate more easily.
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Figure 3-11
Quick Demo Place 3.5 g of sulfur powder and 6.0 g of iron filings in separate weighing dishes. Have students record the physical properties of each substance. Hold a magnet underneath the dish of iron filings to demonstrate magnetic properties. Combine the two dishes and stir with a glass rod, then pour into a test tube. Heat the test tube strongly. CAUTION: Wear goggles and perform in fume hood! Once the reaction is complete, plunge the test tube into a beaker of cold water. The test tube will crack and you will be able to retrieve the iron sulfide product using forceps. Show that the physical properties have changed and weigh the isolated iron sulfide chunks. The iron sulfide is a
Lavoisier’s experimental decomposition of mercury(II) oxide is one proof of the law of conservation of mass. Although a chemical reaction is obvious (powder to liquid mercury), matter was neither created nor destroyed.
chemical reaction. When the reaction is performed in a closed container, the oxygen gas cannot escape and the mass before and after the reaction can be measured. The masses will be the same. Mercury(II) oxide yields mercury oxygen 200 g 16 g 216 g mass of products Mass of reactant A more modern digital analytical balance can be used to prove the conservation of mass of this example. The law of conservation of mass is one of the most fundamental concepts of chemistry. Let’s examine more closely some situations that illustrate the concept. Example Problem 3-1 leads you through a sample calculation. The practice problems also illustrate the law of conservation of mass.
gray, P nonmagnetic solid; the mass should be close to 9.5 g.
LS PROBLEMS Have students refer to Appendix D for complete solutions to Practice Problems. 6. 89.4 g 7. 24.1 g of chlorine gas is
Mercury occurs naturally in air, water, soil, and living organisms. Seafood that is intended for human consumption is monitored to ensure that the products do not contain levels of mercury exceeding the established limits for public safety.
EXAMPLE PROBLEM 3-1 Conservation of Mass In an experiment, 10.00 g of red mercury(II) oxide powder is placed in an open flask and heated until it is converted to liquid mercury and oxygen gas. The liquid mercury has a mass of 9.26 g. What is the mass of oxygen formed in the reaction? 1. Analyze the Problem
used in the reaction. Because the sodium reacts with excess chlorine, all of the sodium (15.6 g) is used in the reaction. 8. 91.5 g of bromine reacted and 101.8 g of aluminum bromide were formed. 9. 6.6 g
You are given the mass of a reactant and the mass of one of the products in a chemical reaction. Applying the law of conservation of mass, the total mass of the products must equal the total mass of the reactants. This means that the mass of the liquid mercury plus the mass of the oxygen gas must equal the mass of the mercury(II) oxide powder.
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Known
Unknown
Mass of mercury(II) oxide 10.00 g Mass of liquid mercury 9.26 g
Mass of oxygen formed ?g
Chapter 3 Matter—Properties and Changes
CHEMISTRY JOURNAL The Conservation of Energy Linguistic The law of conservation of matter, formalized by Lavoisier, was a major achievement for the eighteenth century. However, it is really an incomplete statement without considering it with the
law of conservation of energy. Have students research and write a short report on the experiments of the twentieth century that P led to the formulation of the law of conservation of energy. L2
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3 Assess
2. Solve for the Unknown Write an equation showing conservation of mass of reactants and products.
Check for Understanding
Massreactants Massproducts Massmercury(II) oxide Massmercury Massoxygen Solve the equation for Massoxygen. Massoxygen Massmercury(II) oxide Massmercury Substitute known values and solve. Massoxygen 10.00 g 9.26 g Massoxygen 0.74 g 3. Evaluate the Answer The sum of the masses of the two products equals the mass of the reactant, verifying that mass has been conserved. The answer is correctly expressed to the hundredths place.
PRACTICE PROBLEMS 6. From a laboratory process designed to separate water into hydrogen and oxygen gas, a student collected 10.0 g of hydrogen and 79.4 g of oxygen. How much water was originally involved in the process? 7. A student carefully placed 15.6 g of sodium in a reactor supplied with an excess quantity of chlorine gas. When the reaction was complete, the student obtained 39.7 g of sodium chloride. How many grams of chlorine gas reacted? How many grams of sodium reacted?
e! Practic
For more practice with conservation of mass, go to Supplemental Practice Problems in Appendix A.
8. In a flask, 10.3 g of aluminum reacted with 100.0 g of liquid bromine to form aluminum bromide. After the reaction, no aluminum remained, and 8.5 grams of bromine remained unreacted. How many grams of bromine reacted? How many grams of compound were formed? 9. A 10.0-g sample of magnesium reacts with oxygen to form 16.6 g of magnesium oxide. How many grams of oxygen reacted?
Visual-Spatial Set up simultaneous experiments. In one small beaker, place a scoop of baking soda (sodium hydrogen carbonate) and add 10 mL of vinegar (acetic acid). Invert another larger beaker over the top to capture the carbon dioxide–water that is produced. In the second experiment, pour several mL of carbonated beverage (club soda) into a small beaker and place on a hotplate. Again, invert a larger beaker over the top of the smaller beaker to capture the carbon dioxide–water that is produced. When both reactions are complete, slide a glass plate under each inverted beaker and test for the presence of carbon dioxide by extinguishing a splint or candle. Ask the students how the first experiment is different from the second. The first experiment generates carbon dioxide through a chemical change, the second through a physical change.
Reteach Section
3.2
Assessment
10.
Describe the results of a physical change and list three examples of physical change.
11.
Describe the results of a chemical change. List four indicators of chemical change.
12.
Solve each of the following. In the complete reaction of 22.99 g of sodium with 35.45 g of chlorine, what mass of sodium chloride is formed? b. A 12.2-g sample of X reacts with a sample of Y to form 78.9 g of XY. What is the mass of Y that reacted? a.
13.
Thinking Critically A friend tells you, “Because composition does not change during a physical change, the appearance of a substance does not change.” Is your friend correct? Explain why.
14.
Classifying Classify each of the following examples as a physical change or a chemical change. crushing an aluminum can recycling used aluminum cans to make new aluminum cans c. aluminum combining with oxygen to form aluminum oxide a.
b.
Set up a beaker of water and another beaker of ethanol. Place several ice cubes in each beaker. Ask students to relate their observations to the physical states of the matter involved. The ice will float on the water because the solid is less dense than the liquid; however, ice is more dense than liquid ethanol and will sink. To dispose of ethanol, evaporate under a hood.
Assessment 3.2 Changes in Matter
Section 3.2
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Assessment
10. During a physical change, a substance is altered but its composition does not change. Examples will vary but may include changes such as melting, freezing, boiling, bending, and tearing. 11. During a chemical change, the composition of a substance is altered. Possible indicators of chemical change include a change in color, odor, or
temperature, and the formation of a gas or solid from a liquid. 12. a. 58.44 g of sodium chloride b. 66.7 g of Y 13. The statement is false. While the composition does not change, a change in appearance often accompanies a physical change. 14. a. physical; b. physical; c. chemical
Knowledge Set out a tray
of objects (glassware, files, clamps, splints). Have the students team up and choose three objects from the tray and list the physical properties of each object and some physical changes that the object could undergo. Repeat for chemical properties and changes. L2 ELL COOP LEARN P
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Section
Section 3.3
Objectives
1 Focus
• Contrast mixtures and substances.
Focus Transparency Before presenting the lesson, display Section Focus Transparency 11 on the overhead projector. Have students answer the accompanying questions using Section Focus Transparency Master 11. L1 ELL
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3.3
Mixtures
Use with
n 3.3 3, Sectio Chapter
B
• Classify mixtures as homogeneous or heterogeneous. • List and describe several techniques used to separate mixtures.
Vocabulary mixture heterogeneous mixture homogeneous mixture solution filtration distillation crystallization chromatography
A
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P Figure 3-12
C
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Copyright
of the McGr a division Graw-Hill, © Glencoe/Mc
anies, aw-Hill Comp
Inc.
a The components of the sand and water mixture (left) are obvious, whereas the components of the table salt and water mixture (right) are not. b The salt component becomes obvious when the mixture is boiled.
de? raph B ma in photog tance in e liquid the subs How is th on with mm co have in C? t does it ograph 2 Wha A? Phot h rap photog
1
Mixtures of Matter When scientists speak of the composition of matter, they are referring to the kinds and amounts of components of which the matter is made. On the basis of composition alone, all matter can be classified into two broad categories: substances or mixtures. You have already learned that a pure substance is a form of matter with a uniform and unchanging composition. You also know that the intensive properties of pure substances do not change, regardless of the physical state or amount of the substance. But what is the result when two or more substances are combined?
Mixtures A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties. The composition of mixtures is variable, and the number of mixtures that can be created by combining substances is infinite. Although much of the focus of chemistry is the behavior of substances, it is important to remember that most everyday matter occurs as mixtures. Substances tend naturally to mix; it is difficult to keep things pure. Two mixtures, sand and water, and table salt and water, are shown in Figure 3-12a. You know water to be a colorless liquid. Sand is a grainy solid that does not dissolve in water. When sand and water are mixed, the two substances are in contact, yet each substance retains its properties. The sand and water have not reacted. Just by looking at the sand–water mixture in beaker A, it is easy to see each separate substance. Some mixtures, however, may not look like mixtures at all. The mixture of table salt and water in the beaker labeled B is colorless and appears the same as pure water. How can you determine if it is a mixture? If you were to boil away the water, you would see a white residue. That residue, shown in Figure 13-12b, is the salt. Thus, the colorless mixture actually contained two separate substances. The salt and the water physically mixed but did not react and were separated by the physical method of boiling.
sparencies Focus Tran Section
Change Matter and Chemistry:
2 Teach Assessment Portfolio Have the students look around the room and generate a list of items that are mixtures and items that are substances. Have them identify the criteria they are using for classification and rough percentages of each item in each category. Lists can be placed in their portfolios. Answers will vary but there are usually higher percentages of materials that are classified as mixtures. L2 P
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Chapter 3 Matter—Properties and Changes
M EETING I NDIVIDUAL N EEDS Visually Impaired Kinesthetic Set up stations with examples of heterogeneous and homogeneous mixtures that can be discerned by touch. Partner visually impaired students with sighted students and have them rotate through the stations P to classify each type of mixture. L1 ELL
Resource Manager Study Guide for Content Mastery, p.16 L2 Solving Problems: A Chemistry Handbook, Section 3.3 L2 Section Focus Transparency 11 and Master L1 ELL
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Types of mixtures The combinations of pure substances shown in Figure 3-12 are indeed both mixtures, despite their obvious visual differences. Can you think of some way to further define mixtures? Mixtures themselves are classified as either heterogeneous or homogeneous. A heterogeneous mixture is one that does not blend smoothly throughout and in which the individual substances remain distinct. The sand and water mixture is an example of a heterogeneous mixture. Suppose you draw a drop from the top of the mixture using an eyedropper. The drop would be almost completely water. If you draw a second drop from the bottom of the mixture, that drop would contain mostly sand. Thus the composition of the sand–water mixture is not uniform— the substances have not blended smoothly and the two substances of the mixture (sand on the bottom and water on the top) remain distinct. In another example, fresh-squeezed orange juice is a mixture of juice and pulp. The pulp component floats on top of the juice component. Is your favorite pizza a mixture? The answer is yes when you consider that the pizza is a combination of distinct areas of dough, sauce, cheese, and toppings. We can therefore say that the existence of two or more distinct areas indicates a heterogeneous mixture. A homogeneous mixture has constant composition throughout; it always has a single phase. Let’s examine the salt–water mixture using the eyedropper. A drop of the mixture from the top of the beaker has the same composition as a drop from the bottom of the beaker. In fact, every drop of the mixture contains the same relative amounts of salt and water. Homogeneous mixtures are also referred to as solutions. You are probably most familiar with solutions in a liquid form, such as cough suppressant medicine and lemonade, but solutions may contain solids, liquids, or gases. Table 3-3 lists the various types of solution systems and gives an example of each. Solutions are very important in chemistry, and, in fact, this textbook devotes an entire chapter to the study of solutions. The solid–solid solution known as steel is called an alloy. An alloy is a homogeneous mixture of metals, or a mixture of a metal and a nonmetal in which the metal substance is the major component. The U.S. Mint’s golden dollar coin, shown in Figure 3-13, uses a metal alloy composed of 77% copper, 12% zinc, 7% manganese, and 4% nickel surrounding a copper core. Alloys are also used in spacecraft and automobiles. What might be the benefit of using alloys for these applications? Manufacturers combine the properties of various metals in an alloy to achieve greater strength and durability of their products.
Quick Demo The Tyndall effect is a quick test that differentiates a solution from a heterogeneous mixture. Shine a thin beam of light (a laser is ideal) through a beaker containing a solution such as copper sulfate or sodium chloride; the beam will not be visible because of the small size of the solute particles (smaller than 106 mm). However, when you shine light through a mixture such as a weak milk colloid or clay suspension, the particles are large enough (greater than 106 mm) to P refract the beam; thus, the beam is plainly visible.
LS Applying Chemistry Figure 3-13 Coins issued by the U.S. Mint are metal alloys. The combination of multiple metals gives the coins specific properties such as color, weight, and durability.
Table 3-3 Types of Solution Systems System
Example
Gas–gas
Air is primarily a mixture of nitrogen, oxygen, and argon gases.
Gas–liquid
Carbonated beverages contain carbon dioxide gas in solution.
Liquid–gas
Moist air contains water droplets in air (which is a mixture of gases).
Liquid–liquid Vinegar contains acetic acid in water. Solid–liquid
Sweetened powder drink contains sugar and other solid ingredients in water.
Solid–solid
Steel is an alloy of iron containing carbon.
3.3 Mixtures of Matter
Silver mining does not yield pure silver metal. In fact, the highest percentage of silver is found mixed in lead ores, frequently called lead bullion. The silver is removed by adding small amounts of zinc to the molten bullion; the zinc alloys with the silver and floats to the surface where it is skimmed off, leaving the lead. In areas where silver mining was once a major activity, housing developments and other public communities now sit on old mine sites. In the mid 1980s, the Environmental Protection Agency considered an effort to clean up some former silver mine sites. However, it was determined that residents were not experiencing a higher health risk and “stirring up” the areas could cause greater risk.
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CHEMISTRY JOURNAL Separating a Mixture Visual-Spatial Pass around a small sandwich bag containing a mixture such as styrofoam chunks, sand, copper sulfate, and iron filings and ask students to design a branching flowchart that shows how the mixture could be separated without physically picking out the pieces. They may
use the CRC Handbook of Chemistry and Physics to develop their separation methods. After they have submitted their flowchart, they may proceed to actually carrying out P the experiment and writing it up. L2 ELL
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Separating Mixtures
mini LAB P Purpose
To separate a mixture by paper chromatography
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Process Skills
Applying concepts, collecting and interpreting data, comparing and contrasting, observing and inferring Safety Precautions
Be sure students wear safety goggles and aprons. Teaching Strategies
• Remind students to handle the filter paper as little as possible. The oil from their fingers will distort the results. • Any size of round filter paper will work. Green and yellow dyes separate best if the paper is relatively large in diameter. • Use several different types of black felt pens and black markers. Each brand and type has different ink combinations. This makes it more interesting when students compare their chromatograms. The inks must be water soluble. Expected Results
As the water spreads out on the paper, different dyes in the ink will spread out from the center and be deposited on the filter paper at different distances from the center. Analysis
1. Drawings should resemble the miniLab photo with correct labels. 2. Different components of the ink have varying attraction for the filter paper. Therefore, the colors that comprise the ink will be deposited at different distances from the center of the paper. 3. Answers will vary. Different makes and types of black ink have different dyes in them.
Figure 3-14 The physical properties of the iron filings on the plate allow them to be easily separated from the sand using a magnet.
miniLAB Separating Ink Dyes Applying Concepts Chromatography is an important diagnostic tool for chemists. Many types of substances can be separated and analyzed using this technique. In this experiment, you will use paper chromatography to separate the dyes in water-soluble black ink.
Materials 9-oz wide-mouth plastic cups (2); round filter paper; 1⁄4 piece of 11-cm round filter paper; scissors; pointed object, approximately 3–4 mm diameter; water-soluble black felt pen or marker Procedure 1. Fill one of the wide-mouth plastic cups with water to about 2 cm from the top. Wipe off any water drops on the lip of the cup. 2. Place the round filter paper on a clean, dry surface. Make a concentrated ink spot in the center of the paper by firmly pressing the tip of the pen or marker onto the paper. 3. Use a sharp object to create a small hole, approximately 3–4 mm or about the diameter of a pen tip, in the center of the ink spot. 4. Roll the 1/4 piece of filter paper into a tight cone. This will act as a wick to draw the ink. Work the pointed end of the wick into the hole in the center of the round filter paper. 5. Place the paper/wick apparatus on top of the cup of water, with the wick in the water. The
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water will move up the wick and outward through the round paper. 6. When the water has moved to within about 1 cm of the edge of the paper (about 20 minutes), carefully remove the paper from the water-filled cup and put it on the empty cup.
Analysis 1. Make a drawing of the round filter paper and
label the color bands. How many distinct dyes can you identify? 2. Why do you see different colors at different locations on the filter paper? 3. How does your chromatogram compare with those of your classmates who used other types of black felt pens or markers? Explain the differences.
Chapter 3 Matter—Properties and Changes
Resource Manager
Assessment Skill Have students repeat the experiment using ethanol and permanent markers. Have them write a summary of both experiments in which they compare and contrast the results. L2
Most matter exists naturally as mixtures. For students and scientists to gain a thorough understanding of matter, it is very important to be able to do the reverse of mixing, that is, to separate mixtures into their component substances. Because the substances in a mixture are physically combined, the processes used to separate a mixture are physical processes that are based on the difference in physical properties of the substances. Sometimes it is very easy to separate a mixture; separating a mixture of pennies and nickels is not a difficult task. More difficult would be separating a mixture of sand and iron filings. Or would it be? The demonstration illustrated in Figure 3-14 shows how the sand–iron mixture is easily separated on the basis of the unique physical properties of the substances involved. Numerous techniques have been developed that take advantage of different physical properties in order to separate mixtures. Heterogeneous mixtures composed of solids and liquids are easily separated by filtration. Filtration is a technique that uses a porous barrier to separate a solid from a liquid. As Figure 3-15 shows, the mixture is poured through a piece of filter paper that has been folded into a cone shape. The liquid passes through, leaving the solids trapped in the filter paper.
ChemLab and MiniLab Worksheets, p. 9 L2 Small-Scale Laboratory Manual, pp. 9–12 L2 Forensics Lab Manual, pp. 1–12 L2
P
CD-ROM Chemistry: Matter and Change Exploration: Separating Mixtures Experiment: Metal Alloys
Figure 3-15 Filtration is a common technique used to remove impurities from drinking water. Clean water passes through the porous filter a , leaving behind the impurities that can be easily discarded b .
a
b
Most homogeneous mixtures can be separated by distillation. Distillation is a separation technique that is based on differences in the boiling points of the substances involved. In distillation, a mixture is heated until the substance with the lowest boiling point boils to a vapor that can then be condensed into a liquid and collected. When precisely controlled, distillation can separate substances having boiling points that differ by only a few degrees. Did you ever make rock candy as a child? Making rock candy from a sugar solution is an example of separation by crystallization. Crystallization is a separation technique that results in the formation of pure solid particles of a substance from a solution containing the dissolved substance. When the solution contains as much dissolved substance as it can possibly hold, the addition of a tiny amount more often causes the dissolved substance to come out of solution and collect as crystals on some available surface. In the rock candy example, as water evaporates from the sugar–water solution, the sugar is left behind as a solid crystal on the string. Crystallization produces highly pure solids. Chromatography is a technique that separates the components of a mixture (called the mobile phase) on the basis of the tendency of each to travel or be drawn across the surface of another material (called the stationary phase). The miniLAB in this section describes how you can separate a solution such as ink into its components as it spreads across a stationary piece of paper. The separation occurs because the various components of the ink spread through the paper at different rates.
Section
3.3
How do mixtures and substances differ?
16.
Consider a mixture of water, sand, and oil. How many phases are present? How could you separate this mixture into individual substances?
17.
18.
Classify each of the following as either a heterogeneous or homogeneous mixture. a. b. c. d. e.
orange juice tap water steel (a blend of iron and carbon) air raisin muffin
19.
composition, mixtures do not. Each substance in a mixture retains its own properties, whereas the properties of a substance are different from those of the elements that comprise it. 16. There are three distinct phases, water, sand, and oil. The sand
unknowns in bottles: three of the bottles are solutions (salt water, sugar water, a very dilute milk mixture) and one is a pure substance (distilled water). Ask the students to determine which of the unknowns is a pure substance. L2
of students develop a concept map on an acetate sheet or large sheet of paper. The map should P show the relationships among the following terms: matter, substance, heterogeneous mixture, solid, liquid, gas, vapor, physical change, LS chemical change, homogeneous mixture, solution, alloy. L2 COOP LEARN P
Assessment
Thinking Critically When 50 mL of ethanol is mixed with 50 mL of water, a solution forms. The volume of the final solution is less than 100 mL. Propose an explanation for this phenomenon. (Hint: Consider what you know about the space between particles in liquids.) Applying Concepts Describe the separation technique that could be used to separate each of the following mixtures. two colorless liquids a nondissolving solid mixed with a liquid c. red and blue marbles of same size and mass a.
b.
Skill Set up samples of solutions, colloids, and suspensions LSdialysis bags or tubing P(with the in ends tied) and suspend them in beakers of distilled water. Ask students to classify the samples and LS with support their classifications diagrams or written explanations in their portfolios. Solutions have particles small enough to fit through the pores of a dialysis tube. This will be evident by the coloration of the distilled water outside the dialysis tubing (if you are using a species with color, such as copper sulfate) or by testing with a conductivity apparatus (if you are using a colorless species, such as sodium chloride). L2 P
69
LS
Assessment
15. Substances have a constant
Kinesthetic Set out four
Interpersonal Have teams
3.3 Mixtures of Matter
Section 3.3
Check for Understanding
Reteach
Assessment
15.
3 Assess
could be separated from the oil and water by filtration. The oil and water could be separated by pouring the oil off the top of the water, or by distillation. 17. a. heterogeneous; b. homogeneous; c. homogeneous; d. homogeneous; e. heterogeneous
18. Particles of liquids have space
P between them. When the two liquids mix, particles of one liquid fit between particles of the other liquid. LS 19. a. distillation b. filtration c. manually separating the 69 marbles by color
Section
Section 3.4
Objectives
1 Focus
• Distinguish between elements and compounds.
Focus Transparency Before presenting the lesson, display Section Focus Transparency 12 on the overhead projector. Have students answer the accompanying questions using Section Focus Transparency Master 12. L1 ELL
P Focus Section
12
ncy Transpare
Elements Common unds po m Co tion 3.4 d an pter 3, Sec with Cha
e of Elem
Abundanc
3.4
• Describe the organization of elements on the periodic table. • Explain how all compounds obey the laws of definite and multiple proportions.
Vocabulary element periodic table compound law of definite proportions percent by mass law of multiple proportions
Use
t
rth’s Crus
ents in Ea
LS
P Silicon 25.7%
Aluminum 8.1%
Figure 3-16
LS
Although many early scientists have contributed to the modern organization of the elements, Mendeleev’s system of rows and columns was a revolutionary advancement.
3.4% Calcium 2.6% ements 2.6% Other el Sodium m 2.4% Potassiu m 1.9% siu ne ag M ’s crust? in Earth abundant some the most de up of ment is at are ma Which ele items th on mm some co are t ha s? 2 W element of these
Copyright
of the McGr a division Graw-Hill, © Glencoe/Mc
anies, aw-Hill Comp
Inc.
Iron 4.7%
Oxygen 49.2%
To this point you’ve examined many of the properties of matter. You’ve also learned how scientists have organized, classified, and described matter by arranging it into various subcategories of components. But there remains another fundamental level of classification of matter: the classification of pure substances as elements or compounds.
Elements Recall that earlier in this chapter you considered the diversity of your surroundings in terms of matter. Although the diversity is astounding, in reality all matter can be broken down into a relatively small number of basic building blocks called elements. An element is a pure substance that cannot be separated into simpler substances by physical or chemical means. On Earth, 91 elements occur naturally. Copper, oxygen, and gold are examples of naturally occurring elements. There are also several elements that do not exist naturally but have been developed by scientists. Each element has a unique chemical name and symbol. The chemical symbol consists of one, two, or three letters; the first letter is always capitalized and the remaining letter(s) are always lowercase. Why has so much effort been given to naming the elements? The names and symbols of the elements are universally accepted by scientists in order to make the communication of chemical information possible. The 91 naturally occurring elements are not equally abundant. For example, hydrogen is estimated to make up approximately 75% of the mass of the universe. Oxygen and silicon together comprise almost 75% of the mass of Earth’s crust, while oxygen, carbon, and hydrogen account for more than 90% of the human body. Francium, on the other hand, is one of the least abundant naturally occurring elements. It is estimated that there is probably less than 20 grams of francium dispersed throughout Earth’s crust. To put that into perspective, the total mass of francium is approximately equal to the mass of your pencil or pen. A first look at the periodic table As many new elements were being discovered in the early nineteenth century, chemists began to see patterns of similarities in the chemical and physical properties of particular sets of elements. Several schemes for organizing the elements on the basis of these similarities were proposed, with varying degrees of success. In 1869, the Russian chemist Dmitri Mendeleev made a significant contribution to the effort. Mendeleev devised the chart shown in Figure 3-16, which organized all of the elements that were known at the time into rows and columns based on their similarities and their masses. Mendeleev’s organizational table was the first version of what has been further developed into the periodic table of elements. The periodic table organizes the elements into a grid of horizontal rows called periods and vertical columns called groups or families. Elements in the same group have similar chemical and physical properties. The table is called “periodic” because the pattern of similar properties repeats as you move from period to period. One of the brilliant aspects of Mendeleev’s original table was that its structure could accommodate elements that did not even exist at
1
sparencies Focus Tran Section
Change Matter and Chemistry:
2 Teach
VIDEODISC Cosmic Chemistry Disc 3, Side 6 and Disc 4, Side 8 Still: Elements
{`@±Å‘} {`@±ë’} {`@±°÷}
Elements and Compounds
70
Chapter 3 Matter—Properties and Changes
M EETING I NDIVIDUAL N EEDS Learning Disabled Visual-Spatial Decide which of the elements’ symbols and name spellings you wish your students to know (generally 50 to 60 of the more commonly used elements). Have students make flashcards
with the name of the element on one side and its corresponding symbol on the back. Provide some class time for students to quiz each other using the flashcards. L1 ELL
P
70
the time. Notice the blank spots in Mendeleev’s table. By analyzing the similarities among the elements and their pattern of repetition, Mendeleev was able to predict the properties of elements that were yet to be discovered. In most cases, Mendeleev’s predictions (and the blanks in the table) closely matched the characteristics of new elements as they were discovered. Figure 3-18 on pages 72–73 shows samples of the elements in their arrangement in the periodic table. The standard modern version of the periodic table includes more than 100 elements. You’ll study the periodic table in greater detail later in this textbook. In fact, the periodic table remains a dynamic tool as scientists continue to discover new elements.
Quick Demo Using a Hoffman apparatus, show the electrolysis of water emphasizing the constant 2:1 ratio of the volumes of hydrogen to oxygen. You may also wish to drain off a test-tube amount of each gas and perform a lighted splint test on the hydrogen (it and a glowing splint barks) P test on the oxygen (it relights).
Compounds Take a moment to recall what you have learned about the organization of matter, using Figure 3-17 as a guide. You know that matter is classified as pure substances and mixtures. As you learned in the previous section, mixtures can be homogeneous or heterogeneous. You also know that elements are pure substances that cannot be separated into simpler substances. There is yet another classification of pure substances—compounds. A compound is a combination of two or more different elements that are combined chemically. Most of the substances that you are familiar with and, in fact, much of the matter of the universe are compounds. Water, table salt, table sugar, and aspirin are examples of common compounds. Today, there are approximately 10 million known compounds, and new compounds continue to be developed and discovered at the rate of about 100 000 per year. Can you recall some of the medicinal compounds that have made headlines in recent years? There appears to be no limit to the number of compounds that can be made or that will be discovered. Considering this virtually limitless potential, several organizations have assumed the task of collecting data and indexing the known chemical compounds. These organizations maintain huge databases that allow researchers to access information on existing compounds. The databases and retrieval tools enable scientists to build the body of chemical knowledge in an efficient manner. The chemical symbols of the periodic table make it easy to write the formulas for chemical compounds. For example, table salt, or sodium chloride, is composed of one part sodium (Na) and one part chlorine (Cl), and its chemical formula is NaCl. Water is composed of two parts hydrogen (H) to one part oxygen (O), and its formula is H2O. Figure 3-17
Matter
Mixtures
LS
Physical changes
The concept of matter is farreaching and can be overwhelming. But, when broken down as shown here, it becomes clear how elements, compounds, substances, and mixtures define all matter.
Pure substances
Chemical changes
Heterogeneous mixtures
Homogeneous mixtures
Elements
Compounds
dirt, blood, milk
lemonade, gasoline, steel
oxygen, gold, iron
salt, baking soda, sugar
3.4 Elements and Compounds
Resource Manager Study Guide for Content Mastery, pp. 17–18 L2 Solving Problems: A Chemistry Handbook, Section 3.4 L2 Section Focus Transparency 12 and Master L1 ELL Teaching Transparency 9 and Master L2 ELL P
P
71
CHEMISTRY JOURNAL Elementary Patterns Intrapersonal Have students research the work of scientists who, like Mendeleev, worked in the area of assigning meaningful patterns among the elements. Some of these scientists include P Dobereiner, Newlands, Meyer, Moseley, and Seaborg. L2
Pages 68–71 1(A), 4(C), 4(D), 6(C), 11(A)
71
LS
IA 1
Reinforcement
Periodic Table
Interpersonal Reinforce
students’ knowledge of elemental symbols by playing “Bowling for Elements.” Insert ten element flashcards in pinlike formation in pockets of a large cardboard or on the chalkboard. Divide the class into teams and have individuals take turns naming as many of the element “pins” by moving from the lead pin to any contiguous pin. Keep score as in P bowling. L1 ELL COOP LEARN
1
1
2
6,9
3
3
P
Extension LS
1,0
23,0
11
P
Intrapersonal Dmitri
4
Mendeleev (1834–1907) was LS a delegate at the First International LS in 1860, and Chemistry Congress from that experience he began the P undertaking that would immortalize him in the history of chemistry. Have students use the Internet and other LS resources to learn about the meetings for chemists and scientists that take place today. L2
39,1
19
5
85,5
132,9
55
VIDEODISC Cosmic Chemistry Disc 3, Side 6 and Disc 4, Side 8 Still: Periodic table
7
P
Li
9,0
4
Na
24,3
K
40,1
12
20
Be
Mg
Ca
IIIB 3
45,0
21
Sc
IVB 4
47,9
22
Ti
VB 5
50,9
23
V
VIB 6
52,0
24
VIIB 7
54,9
Cr
25
Mn
VIII 9
8
55,8
26
Fe
58,9
Ru
102,9
Os
192,2
27
Rb
87,6
Cs
137,3
22 min 223
87
Fr
38
56
Sr
Ba
1600 a 226
88
Ra
88,9
39
138,9
57
Y
La
22 a 227
89
Ac
91,2
40
178,5
72
Zr
92,9
Hf
180,9
65 s 261
104
Rf
41
73
Nb
Ta
34 s 262
105
Db
95,9
42
183,8
74
Mo
W
98
43
186,2
75
21 s 266
106
Tc
101,1
Re
190,2
44
76
440 ms
Sg
264
107
Bh
45
77
9,3 s 269
108
Rh
Ir
70 ms
Hs
268
109
Mt
LS
{`@±¡ÿ} {`@±—Ÿ} Pages 72–73 4(D)
18 a
Figure 3-18 The periodic table shown above illustrates samples of many of the elements. Be sure to use the periodic table on pages 156-157 for reference throughout your chemistry course.
72
138,9
57
La
22 a 227
89
Ac
140,1
58
Ce
140,9
59
Pr
144,2
60
Nd
Our understanding of the elements has changed drastically in the past 2500 years. The ancient Greek philosophers believed that all the elements of the universe were combinations of water, air, earth, and fire. Aristotle suggested a
232
90
Th
231
91
Pa
238
92
U
Chapter 3 Matter—Properties and Changes
fifth element, “aether,” of which all the heavens were made. The philosopher Democritus (470–380 B.C.) was the first to believe that all matter consisted of tiny particles and coined the term “atomos” meaning “indivisible.”
145
61
Pm
1,4·1010a 3,3·104a 4,5·109a 2,1·106a
The History of Elements
72
Co
4,2·106a
37
6
H
IIA 2
Egyptian practices in chemistry combined with Greek philosophy and mathematics to form the science of “khemia.” The Arabs inherited these traditions and placed the “al-“ before the name, forming the pseudoscience “alchemy.”
237
93
Np
VIIIA 18
of the Elements IIIA 13
IVA 14
Visual Learning Visual-Spatial Have the
VA 15
VIA 16
VIIA 17
4,0
2
He
students use the periodic table to determine the number of elements that are gaseous, liquid, solid, metallic, and radioactive at room temperature. L2
Assessment 10,8
5
IB 11
10
58,7
28
106,4
46
Ni
63,5
Pd
107,9
29
47
IIB 12
Cu
65,4
Ag
112,4
30
48
27,0
13
Zn
69,7
Cd
114,8
31
49
B
12,0
Al
28,1
Ga
72,6
6
In
14
32
118,7
50
C
14,0
Si
31,0
Ge
74,9
Sn
121,8
7
15
33
51
N
16,0
P
32,1
As
79,0
Sb
127,6
8
16
34
52
O
19,0
S
35,5
Se
79,9
Te
126,9
17
102 a 195,1
78
Pt
197,0
79
118 ms
Au
200,6
1,5 ms
80
Hg
204,4
81
Tl
207,2
82
Pb
209,0
83
Bi
209
84
9
Po
35
53
F
20,2
Cl
39,9
Br
83,8
I
8,1 h 210
85
At
10
18
36
131,3
54
Ne
Ar
Kr
Xe
3,8 d 222
86
Rn
Skill Have students use the CRC Handbook of Chemistry and Physics (section on element inforP following mation) to research the sample questions about the elements. • How many elements are named LS Cities or for people? Countries? states? • How many elements are named for mythological figures or gods? • What town has four elements named for it? • What elements were known to ancient humans? • What elements were discovered before 1800? Between 1801 and 1900? Between 1901 and the present? Ask the students to choose one particular category and portray the information graphically. L2
0,24 ms
273
272
277
110
111
112
P
150,4
62
Sm
152,0
63
Eu
157,3
64
Gd
158,9
65
Tb
8,0·107a 7400 a 1,6·107a 1400 a 244
94
Pu
243
95
Am
247
96
Cm
247
97
Bk
162,5
66
Dy
900 a 251
98
Cf
164,9
67
Ho
472 d 252
99
Es
167,3
68
Er
101 d 257
100
168,9
69
Tm
52 d
173,0
70
Yb
58 min
Fm 101 Md 102 No 258
259
175,0
71
3,6 h 262
103
Lr
3.4 Elements and Compounds
Alchemists sought to find a mysterious substance that could be taken apart and recombined to form more precious elements, such as gold. Although the practice of alchemy was a dead end in itself, much useful chemical information and
LS
Lu
many processes were stumbled upon. Early Chinese philosophers believed that all materials cycle through five fundamental stages: earth, wood, fire, metal, and water. Each step of the cycle led to a state of greater order. For
73
instance, the earth allows a tree to grow, which in turn can be chopped down and burned to transform metals.P In the heating process, condensation provides the water to renew the cycle.
LS 73
Enrichment Intrapersonal Have each
student “adopt” an element and prepare a report on the properties, uses, abundance, method of mining and purifying, costs, and other pertinent information. Students can present a report per class, per week, or simply be “on-call” as the resident expert on that element when the discussion merits it. L2
Figure 3-19 This classic apparatus, called a Hoffman apparatus, and other similar designs are used to separate water into its components.
VIDEODISC P Cosmic Chemistry Disc 2, Side 3 Movie: Electrolysis of Water 0:50 s LS Decomposition reaction
{d…iêT±u} Movie: Sodium Chloride 1:19 min A reaction forming sodium chloride
{`r•E£a‘}
Figure 3-20 Compounds such as sodium chloride (table salt) are often remarkably different from the components that comprise them.
Sodium
Sodium chloride
74
Unlike elements, compounds can be broken down into simpler substances by chemical means. In general, compounds that naturally occur are more stable than the individual component elements. To separate a compound into its elements often requires external energy such as heat or electricity. Figure 3-19 shows the apparatus used to produce the chemical change of water into its component elements of hydrogen and oxygen through a process called electrolysis. Here, one end of a long platinum electrode is exposed to the water in the tube and the other end is attached to a power source. An electric current splits water into hydrogen gas in the compartment on the right and oxygen gas in the compartment on the left. Because water is composed of two parts hydrogen and one part oxygen, there is twice as much hydrogen gas than oxygen gas. The properties of a compound are different from those of its component elements. The example of water in Figure 3-19 illustrates this fact. Water is a stable compound that is liquid at room temperature. When water is broken down into its components, it is obvious that hydrogen and oxygen are dramatically different than the liquid they form when combined. Oxygen and hydrogen are tasteless, odorless gases that vigorously undergo chemical reactions with many elements. This difference in properties is a result of a chemical reaction between the elements. Figure 320 shows the component elements (sodium and Chlorine chlorine) of the compound commonly called table salt (sodium chloride). When sodium and chlorine react with each other, the compound sodium chloride is formed. Note how different the properties of sodium chloride are from its component elements. Sodium is a highly reactive element that fizzes and burns when added to water. Chlorine is a poisonous, pale green gas. Sodium chloride, however, is a white, unreactive solid that flavors many of the foods you eat.
Chapter 3 Matter—Properties and Changes
Internet Address Book Note Internet addresses that you find useful in the space below for quick reference.
Pages 74–75 2(C), 4(C), 5(A)
74
Law of Definite Proportions An important characteristic of compounds is that the elements comprising them combine in definite proportions by mass. This observation is so fundamental that it is summarized as the law of definite proportions. This law states that, regardless of the amount, a compound is always composed of the same elements in the same proportion by mass. For example, consider the compound table sugar (sucrose), which is composed of carbon, hydrogen, and oxygen. The analysis of 20.00 g of sucrose from a bag of sugar is given in Table 3-4. Note that in Column 1 the sum of the individual masses of the elements equals 20.00 g, the amount of sucrose that was analyzed. This demonstrates the law of conservation of mass as applied to compounds: The mass of the compound is equal to the sum of the masses of the elements that make up the compound. Column 2 shows the ratio of the mass of each element to the total mass of the compound as a percentage called the percent by mass. mass of element percent by mass (%) 100 mass of compound Table 3-4 Sucrose Analysis from Bag Sugar Column 1 Element Carbon Hydrogen
Analysis by mass (g)
Column 2 Percent by mass (%)
8.44 g carbon
8.44 g C 100 42.2% carbon 20.00 g sucrose
1.30 g hydrogen
1.30 g H 100 6.50% hydrogen 20.00 g sucrose
Oxygen
10.26 g oxygen
Total
20.00 g sucrose
History
Quick Demo
CONNECTION
A
ntoine-Laurent Lavoisier (1743–1794) is recognized as the father of modern chemistry. While his fellow scientists tried to explain matter based on the elements fire, earth, air, and water, Lavoisier performed some of the first quantitative chemical experiments. His data and observations led to the statement of the law of conservation of mass. He also studied the nature of combustion and devised a system of naming elements. Lavoisier held many public offices in France in which he attempted to reform the French monetary and taxation system and farming methods. He also supervised the French government’s manufacture of gunpowder. During the Reign of Terror that followed the French Revolution, Lavoisier and other members of Fermés Generalé were arrested, tried, and condemned to the guillotine.
CAUTION: Perform this demo under a hood. Weigh any two similarlooking organic compounds of low melting point (sucrose and lactic acid, for example) in separate crucibles and record the mass on the board. Heat each one strongly to drive off the hydrogen and oxygen in the form of water until all that is left is pure carbon. Reweigh the crucibles with the carbon residue and calculate the percentage of carbon in each compound. Ask students if the two compounds could be the same. No, each has a
different percentage of carbon. Next ask students if the percentage of carbon had been the same in each compound, would that prove they were in fact the same compound. No, not neces-
10.26 g O 100 51.30% oxygen 20.00 g sucrose 100.0%
sarily, because the percentages of the other elements in the compound (hydrogen P and oxygen in this case) could be different.
Now let’s suppose you analyzed 500.0 g of sucrose isolated from a sample of sugar cane. The analysis is shown in Table 3-5. Note in Column 2 that the percent by mass values equal those in Column 2 in Table 3-4. Compounds with the same mass proportions must be the same compound; conversely, compounds with different mass proportions must be different compounds. Thus, you can conclude that, although the two samples of sucrose are from different sources, they have the same composition and they must be the same compound.
LS
Table 3-5 Sucrose Analysis from Sugar Cane Column 1 Element Carbon Hydrogen
Analysis by mass (g) 211.0 g carbon 32.5 g hydrogen
Oxygen
256.5 g oxygen
Total
500.0 g sucrose
Column 2 Percent by mass (%) 211.0 g C 100 42.20% carbon 500.0 g sucrose 32.5 g H 100 6.50% hydrogen 500.0 g sucrose 256.5 g O 100 51.30% oxygen 500.0 g sucrose 100.00%
3.4 Elements and Compounds
75
Resource Manager Teaching Transparency 10 and Master L2 ELL
Math Skills Transparency 3 and Master L2 ELL P P P
LS
75
mass percentage is calculated for both compounds, it is found that the composition is not the same for the two compounds; therefore, they must be different. 24. No, you cannot be sure. Having the same mass percentage of a single element does not guarantee that the composition of each compound is the same.
For more practice with percent by mass and law of definite proportions, go to Supplemental Practice Problems in Appendix A.
a
2.000
b
2.000
P
LS
22. If 3.5 g of X reacts with 10.5 g of Y to form the compound XY, what is the percent by mass of X in the compound? The percent by mass of Y?
24. All you know about two unknown compounds is that they have the same percent by mass of carbon. With only this information, can you be sure the two compounds are the same?
Cu
Compound II
1.000
2.000
Mass (g)
Visual-Spatial Have
P
1.000
Cu
Check for Understanding students draw diagrams featuring atoms and molecules that show packing arrangements in heterogeneous mixtures, solutions, and pure substances. L2 ELL
21. If 1.0 g of hydrogen reacts completely with 19.0 g of fluorine, what is the percent by mass of hydrogen in the compound that is formed?
Compound I
Cl
c
3 Assess
20. A 78.0-g sample of an unknown compound contains 12.4 g of hydrogen. What is the percent by mass of hydrogen in the compound?
23. Two unknown compounds are tested. Compound I contains 15.0 g of hydrogen and 120.0 g of oxygen. Compound II contains 2.0 g of hydrogen and 32.0 g of oxygen. Are the compounds the same?
Mass (g)
Have students refer to Appendix D for complete solutions to Practice Problems. 20. 15.9% 21. 5.0% 22. 25% X and 75% Y 23. When the composition by
PRACTICE PROBLEMS e! Practic
Mass (g)
PROBLEMS
Cl
Mass Ratio Comparison
1.000
I II
Figure 3-21 Bar graph a compares the relative masses of copper and chlorine in Compound I and bar graph b compares the relative masses of copper and chlorine in Compound II. c A comparison between the relative masses of copper in both compounds shows a 2:1 ratio.
Law of Multiple Proportions Compounds composed of different elements are obviously different compounds. Can compounds that are composed of the same elements differ from each other? The answer is yes because those different compounds have different mass compositions. The law of multiple proportions states that when different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ratio of small whole numbers. Ratios compare the relative amounts of any items or substances. The comparison can be expressed using numbers separated by a colon or as a fraction. With regard to the law of multiple proportions, ratios express the relationship of elements in a compound. The two distinct compounds water (H2O) and hydrogen peroxide (H2O2) illustrate the law of multiple proportions. Each compound contains the same elements (hydrogen and oxygen). Water is composed of two parts hydrogen (the element that is present in the same amount in both compounds) to one part oxygen (the element that is present in different amounts in both compounds). Hydrogen peroxide is composed of two parts hydrogen and two parts oxygen. Hydrogen peroxide differs from water in that it has twice as much oxygen. When we compare the mass of oxygen in hydrogen peroxide to the mass of oxygen in water, we get the ratio 2:1. In another example, copper (Cu) reacts with chlorine (Cl) under different sets of conditions to form two different compounds. Table 3-6 provides an analysis of their composition. Note that the two copper compounds must be different because they have different percents by mass. Compound I contains 64.20% copper; compound II contains 47.27% copper. Compound I contains 35.80% chlorine; compound II contains 52.73% chlorine. Table 3-6 Analysis Data of Two Copper Compounds
Compound % Cu
LS 76
Mass copper (g) Mass chlorine (g) in 100.0 g of in 100.0 g of % Cl compound compound
Mass ratio mass Cu mass Cl
冢
冣
I
64.20 35.80
64.20
35.80
1.793 g Cu/1 g Cl
II
47.27 52.73
47.27
52.73
0.8964 g Cu/1 g Cl
Chapter 3 Matter—Properties and Changes
CHEMISTRY JOURNAL Same Elements, Major Differences
Pages 76–77 2(C), 3(E), 4(C)
76
Visual-Spatial Have students use the CRC Handbook of Chemistry and Physics to look up the properties of compounds that exemplify the law of multiple proportions (for example, copper(I)
chloride and copper(II) chloride; hydrogen peroxide and water). Have them organize the information in reference tables so they P can clearly see distinctions between the two compounds. L2
LS
Figure 3-22 Analyses of the mass ratios of the two copper chloride compounds shown here indicate that they are indeed different compounds. The calculated mass ratio of compound I to compound II is 2.000 and fits the definition of the law of multiple proportions.
Compare the ratio of the mass of copper to the mass of chlorine for each compound (see the last column of Table 3-6 and Figure 3-21). You’ll notice that the mass ratio of copper to chlorine in compound I (1.793) is two times the mass ratio of copper to chlorine in compound II (0.896).
Assessment
25.
How are elements and compounds similar? How are they different?
26.
What is the basic organizing feature of the periodic table of elements?
27.
Explain how the law of definite proportions applies to compounds.
28.
What type of compounds are compared in the law of multiple proportions?
29.
Thinking Critically Name two elements that have properties similar to those of element potassium (K). To those of krypton (Kr).
30.
Interpreting Data Complete the following table and then analyze the data to determine if compounds I and II are the same compound. If the compounds are different, use the law of multiple proportions to show the relationship between them.
student a 10 cm 10 cm “information square” on which they describe themselves by a category LS height, hair such as name, address, color, eye color, P interests, pets, number of siblings. Have them put a small picture of themselves in the center. Then pass out reduced copies of the completedLSsquares and ask the students to arrange the squares into as many meaningful patterns as possible. Once they have decided on a pattern, students should paste down their squares and describe their pattern in a presentation. This assignment may also be done as an entire class using the original squares and generating discussion about the best placement of each square. In order to obtain enough P squares, consider combining classes. L1 ELL COOP LEARN P
P
Analysis Data of Two Iron Compounds Compound
find it easier to memorize a triangular arrangement of matter from most general at the bottom of the pyramid to most specific (element, compound, solution, heterogeneous mixture) at the top of the pyramid. Also, as you move from right to left on the base of the pyramid, classification becomes more ordered. L1 ELL
P each Kinesthetic Give
As the law of multiple proportions states, the different masses of copper that combine with a fixed mass of chlorine in the two different copper compounds, shown in Figure 3-22, can be expressed as a small whole-number ratio, in this case 2:1. Considering that there is a finite number of elements that exist today and an exponentially greater number of compounds that are composed of these elements under various conditions, it becomes clear how important the law of multiple proportions is in chemistry.
3.4
Visual-Spatial Students may
Extension
1.793 g Cu/g Cl mass ratio compound I 2.000 mass ratio compound II 0.8964 g Cu/g Cl
Section
Reteach
Total mass (g)
Mass Fe (g)
Mass O (g)
I
75.00
52.46
22.54
II
56.00
43.53
12.47
Mass % Fe
Skill Clip photos of various mixtures from magazines or other sources andLS have students identify themLS as heterogeneous mixtures, solutions, or pure substances in P various phases. L2 ELL
Mass % O
3.4 Elements and Compounds
77
LS Section 3.4
AssessmentLS
P
Assessment
25. Compounds are composed of elements and can be broken down. Elements cannot be broken down into simpler substances. 26. The periodic table of elements is organized by similarities in physical and chemical properties. 27. The law of definite proportions
describes the constant composition of a substance. 28. The law of multiple proportions relates the compositions of two compounds composed of the same elements. 29. Elements in group 1A have properties similar to K. Elements in group
8A have properties P similar to Kr.
LS Fe 30. Compound I mass percent
69.95%; mass percent O 30.05%. Compound II mass percent Fe 77.73%; mass percent LS O 22.27%. The compounds are not the same. The mass ratio of compound 1 to compound 2 is 2:3.
77
CHEMLAB P
3
Preparation Time Allotment
One laboratory period LS Process Skills
Observing and inferring, classifying Safety Precautions
Be sure students wear aprons and goggles. Remind students to tie back long hair and use caution around a flame. Paper clip will remain hot for several minutes. Do not allow solutions to contact skin or clothing. Disposal
Rinse filtrate down the drain with lots of water. The solid wastes may be collected for recycling according to local regulations.
CHEMLAB
Matter and Chemical Reactions
O
ne of the most interesting characteristics of matter, and one that drives the study and exploration of chemistry, is the fact that matter changes. By examining a dramatic chemical reaction, such as the reaction of the element copper and the compound silver nitrate in a water solution, you can readily observe chemical change. Drawing on one of the fundamental laboratory techniques introduced in this chapter, you can separate the products. Then, you will use a flame test to confirm the identity of the products.
Problem
Objectives
Materials
Is there evidence of a chemical reaction between copper and silver nitrate? If so, which elements reacted and what is the name of the compound they formed?
• Observe the reactants as they change into product. • Separate a mixture by filtration. • Predict the names of the products.
copper wire AgNO3 solution sandpaper stirring rod 50-mL graduated cylinder 50-mL beaker funnel
• Always wear safety goggles, gloves, and lab apron. • Silver nitrate is toxic and will harm skin and clothing. • Use caution around a flame.
3. A physical property is a charac-
78
filter paper 250-mL Erlenmeyer flask ring stand small iron ring plastic petri dish paper clip Bunsen burner tongs
Safety Precautions
Pre-Lab teristic that can be observed or measured without changing the substance’s composition— for example, color, shape, or mass. A chemical property is the ability of a substance to combine with or change into one or more other substances— for example, reactivity with water. 4. a. You might observe a change in color or odor, the evolution of heat or light, the absorption of energy, or the formation of a gas, liquid, or different solid. A different product will form. b. You might observe a change in shape or in physical state, such as boiling, condensing, freezing, melting, evaporating, dissolving, or crystallizing. 5. A homogeneous mixture is one in which one or more substances are evenly distributed throughout another substance. A heterogeneous mixture is one in which there is an observable separation of component substances.
3
Pre-Lab 1. 2.
Read the entire CHEMLAB. Prepare all written materials that you will take into the laboratory. Be sure to include safety precautions, procedure notes, and a data table in which to record your observations. Reaction Observations
Time (min)
78
Define the terms physical property and chemical property. Give an example of each. 4. Form a hypothesis regarding what you might observe if a. a chemical change occurs. b. a physical change occurs. 5. Distinguish between a homogeneous mixture and a heterogeneous mixture. 3.
Observations
Procedure
Chapter 3 Matter—Properties and Changes
Procedure • The lengths of wire can be cut ahead. • Copper coil can be allowed to sit in AgNO3 solution overnight.
• Darken room to view flame color.
1.
Obtain 8 cm of copper wire. Rub the copper wire with the sandpaper until it is shiny.
2.
Measure approximately 25 mL AgNO3 (silver nitrate) solution into a 50-mL beaker. CAUTION: Do not allow to contact skin or clothing.
3.
Make and record an observation of the physical properties of the copper wire and AgNO3 solution.
CHAPTER 3 CHEMLAB
4.
5.
Coil the piece of copper wire to a length that will fit into the beaker. Make a hook on the end of the coil to allow the coil to be suspended from the stirring rod. Hook the coil onto the middle of the stirring rod. Place the stirring rod across the top of the beaker immersing some of the coil in the AgNO3 solution.
6.
Make and record observations of the wire and the solution every five minutes for 20 minutes.
7.
Use the ring stand, small iron ring, funnel, Erlenmeyer flask, and filter paper to set up a filtration apparatus. Attach the iron ring to the ring stand. Adjust the height of the ring so the end of the funnel is inside the neck of the Erlenmeyer flask.
8.
To fold the filter paper, examine the diagram below. Begin by folding the circle in half, then fold in half again. Tear off the lower right corner of the flap that is facing you. This will help the filter paper stick better to the funnel. Open the folded paper into a cone. Place the filter paper cone in the funnel.
1.
Dispose of materials as directed by your teacher.
2.
Clean and return all lab equipment to its proper place.
3.
Wash hands thoroughly.
Analyze and Conclude 1.
Classifying Which type of mixture is silver nitrate in water? Which type of mixture is formed in step 6? Explain.
2.
Observing and Inferring Describe the changes you observed in step 6. Is there evidence a chemical change occurred? Why?
3.
4.
5. Tear corner 9.
Remove the coil from the beaker and dispose of it as directed by your teacher. Some of the solid product may form a mixture with the liquid in the beaker. Decant the liquid by slowly pouring it down the stirring rod into the funnel. Solid product will be caught in the filter paper. Collect the filtrate—the liquid that runs through the filter paper—in the Erlenmeyer flask.
10.
Transfer the clear filtrate to a petri dish.
11.
Adjust a Bunsen burner flame until it is blue. Hold the paper clip with tongs in the flame until no additional color is observed. CAUTION: The paper clip will be very hot.
12.
Using tongs, dip the hot paper clip in the filtrate. Then, hold the paper clip in the flame. Record the color you observe.
Expected Results
Cleanup and Disposal
6.
Predicting Predict the products formed in step 6. You may not know the exact chemical name, but you should be able to make an intuitive prediction. Using Resources Use resources such as the CRC Handbook of Chemistry and Physics, the Merck Index, or the Internet to determine the colors of silver metal and copper nitrate in water. Compare this information with your observations of the reactants and products in step 6. Identifying Metals emit characteristic colors in flame tests. Copper emits blue-green light. Do your observations in step 12 confirm the presence of copper in the filtrate collected in step 9? Communicating Express in words the chemical equation that represents the reaction that occurred in step 6.
7. Error Analysis
Compare your recorded observations with those of several other lab teams. Explain any differences.
Step 3: Cu – reddish metal; AgNO3– clear, colorless solution Step 6: Solution will turn bluegreen; grayish solid will “grow” on the wire. Step 12: blue-green color
Analyze and Conclude 1. homogeneous; heterogeneous and homogeneous.
2. A grayish solid formed on the
3. 4. 5. 6. 7.
wire. The solution turned bluegreen. Yes, a solid formed and a color change occurred. silver and copper nitrate Silver metal is white to gray. Copper nitrate is blue-green. Experimental results should agree with blue-green light. Copper and silver nitrate solution react to form silver and copper nitrate. Copper wire may not have been clean. The better observations will be more detailed.
Real-World Chemistry 1. Answers will vary but may include analysis of vitamin content, flavors, preservatives, or calorie content.
Real-World Chemistry 1.
Analytical chemists determine the chemical composition of matter. Two major branches of analytical chemistry are qualitative analysis— determining what is in a substance—and quantitative analysis—measuring how much substance. Research and report on a career as an analytical chemist in the food industry.
CHEMLAB
Assessment Portfolio Have each student place the laboratory report for this experiment in his or her portfolio. L2 P
LS
79
P
Resource Manager ChemLab and MiniLab Worksheets, pp. 10–12 L2
LS
Pages 78–79 1(A), 2(A), 2(B), 2(D), 2(E), 5(A)
P
79
CHEMISTRY and
CHEMISTRY and
Society
Society P
Purpose
Green Buildings
Students will learn about efforts to use chemistry LSto produce quality buildings while decreasing their negative impact on the environment.
Until the Industrial Revolution, the amount of carbon dioxide (CO2) in the atmosphere was fairly constant. Since the Industrial Revolution, however, the burning of fossil fuels has contributed to a significant increase in the amount of carbon dioxide in the atmosphere. As the level of carbon dioxide increases, Earth gradually warms up. Too much CO2 in the atmosphere can change the conditions on Earth. Another major source of carbon dioxide may be in the foundation of your building or on the sidewalks near your school. The production of cement, the key ingredient in concrete, releases tremendous amounts of carbon dioxide into the atmosphere. Chemistry may allow engineers to build “green buildings,” that are still practical yet have less of an impact on the environment.
Background While not always thought of among the top industries that pollute the atmosphere, cement production is one of the most energy-intensive industries in the world. This use of energy, along with chemical reactions involved in the production of cement, release huge amounts of carbon dioxide and other greenhouse gases into the atmosphere every year. Annually, cement production releases as much CO2 as 350 million cars. Researchers have found a way to use a waste product of coalburning power plants to decrease the amount of cement used to make concrete. In addition to protecting the environment, the properties of this waste product, known as flyash, lead to a stronger, more durable concrete. Flyash starts out as impurities in coal. Since the impurities cannot be burned, they end up as ash. At high temperatures, they fuse and become glass. As the glass particles move at high speeds with the gases released during the burning of coal, the hot glass turns into tiny beads.
Producing Cement Cement generally begins with a mixture of limestone and sand placed in a kiln, which heats it to about 1480°C. As the mixture is heated, its chemical and physical properties change. After heating, the solid that remains is ground into a fine powder. This is cement. To make concrete, the cement is mixed with fine particles, such as sand, coarse particles, such as crushed stone, and water. During the production of cement, carbon dioxide is released in two ways. First, when the limestone is heated it changes into lime and carbon dioxide. Second, the electrical energy used to heat the kiln is usually supplied by a power plant that burns fossil fuels, such as coal. Fossil fuels also release carbon dioxide and other substances.
One way to reduce the amount of carbon dioxide released into the atmosphere is to find a replacement for cement in concrete. One such replacement is a substance known as flyash. Flyash is a waste product that accumulates in the smokestacks of power plants when ground coal is burned. It is a fine gray powder that consists of tiny glass beads. Using flyash offers several advantages. Flyash ordinarily is dumped in landfills. Replacing cement with flyash can reduce CO2 emissions and prevent
• Ask students to review the green-
80
Investigating the Issue 1.
Communicating Ideas Write a pamphlet for people who are building new homes telling them about the importance of green buildings.
2.
Using the Internet Investigate issues that influence the decision to use flyash. Discuss the advantages and disadvantages of flyash.
Using Flyash
Teaching Strategies house effect and to prepare posters showing how it maintains the temperatures on Earth. • Ask students to debate the possibility of decreasing the amount of concrete used throughout the world. Have them address the issue that the need for cement is expected to double in the next 25 years as developing countries expand their building. • It takes between 1450 and 1600 kg (3200 to 3500 lb) of raw materials to produce about 907 kg
tons of waste from piling up in landfills. Flyash also produces better concrete. Traditional concrete has weak zones where tiny cracks allow water to flow through. Flyash contains fine particles that fill spaces and keep moisture out. Flyash also protects the steel surrounding the concrete, makes the concrete easier to work with, and extends the life of the concrete structure. In fact, flyash is so reliable the Romans used natural materials similar to flyash to build the concrete dome of the Pantheon. Solutions to environmental problems require a willing commitment from scientists, architects, builders, and owners to look for ways to build durable structures and protect the environment.
80
Visit the Chemistry Web site at science.glencoe.com to find links to more information about flyash and green buildings.
Chapter 3 Matter—Properties and Changes
(1 ton) of finished cement. Ask students to research and present other statistics related to cement production. • Some people are concerned about the use of flyash. For example, there is some concern about radioactivity. The EPA believes that flyash does not constitute a significant risk that is any greater than from the cement it replaces. Ask students to find out about any issues related to the use of flyash.
Investigating the Issue 1. Answers will vary. Students should stress the importance of finding industrial methods that are safe for the environment yet still meet the objectives. 2. Students may consider cost, availability, processing ease, and safety in their discussions.
CHAPTER
3
STUDY GUIDE
CHAPTER STUDY GUIDE
3
Using the Vocabulary
Summary 3.1 Properties of Matter
• Solutions are homogeneous mixtures.
• A substance is a form of matter with a uniform and
• Mixtures can be separated by physical means.
unchanging composition. • Physical properties can be observed without altering
a substance’s composition. Chemical properties describe a substance’s ability to combine with or change into one or more new substances. • Both physical and chemical properties are affected by
external conditions such as temperature and pressure. • The three common states of matter are solid, liquid,
and gas.
To reinforce chapter vocabulary, have students write a sentence using each term. L2 ELL
Common separation techniques include filtration, distillation, crystallization, and chromatography. 3.4 Elements and Compounds • Elements are substances that cannot be broken down into simpler substances by chemical or physical means. • The elements are organized in the periodic table of
elements. • A compound is a chemical combination of two or
3.2 Changes in Matter • A physical change alters the physical properties of a substance without changing its composition. • A chemical change, also known as a chemical reac-
tion, involves a change in a substance’s composition.
more elements. Properties of compounds differ from the properties of their component elements. • The law of definite proportions states that a com-
pound is always composed of the same elements in the same proportions. • The law of multiple proportions states that if ele-
• In a chemical reaction, reactants form products.
ments form more than one compound, those compounds will have compositions that are small, whole-number multiples of each other.
• The law of conservation of mass states that mass is
neither created nor destroyed during a chemical reaction; it is conserved.
Review Strategies • Have students summarize P the differences between physical and chemical properties and physical and chemical change and give an example of each.PL2LS • Have students be able to use the symbols of the most frequently used elements. L1 • Have students beLSable to classify matter according to the scheme given in the chapter. L1 P • Problems from Appendix A or the Supplemental Problems booklet can be used for review. L2
LS
3.3 Mixtures of Matter
P
• A mixture is a physical blend of two or more pure
substances in any proportion.
Reviewing Chemistry is a compoP nent of the Teacher Classroom LS Resources package that was P prepared by The Princeton Review. Use the Chapter 3 review materials in this LSbook to review the chapter with your LS students.
Key Equations and Relationships Masselement • percent by mass 100 Masscompound (p. 75)
• law of conservation of mass (p. 63) Massreactants Massproducts
Vocabulary • • • • • • • • • •
chemical change (p. 62) chemical property (p. 57) chromatography (p. 69) compound (p. 71) crystallization (p. 69) distillation (p. 69) element (p. 70) extensive properties (p. 56) filtration (p. 68 ) gas (p. 59)
• • • •
heterogeneous mixture (p. 67) homogeneous mixture (p. 67) intensive properties (p. 56) law of conservation of mass (p. 63) • law of definite proportions (p. 75) • law of multiple proportions (p. 76) • liquid (p. 58)
• • • • • • • • • •
mixture (p. 66) percent by mass (p. 75) periodic table (p. 70) physical changes (p. 61) physical property (p. 56) solid (p. 58) solution (p. 67) states of matter (p. 58) substance (p. 55) vapor (p. 59) Study Guide
81
Portfolio Portfolio
VIDEOTAPE/DVD MindJogger Videoquizzes Chapter 3: Matter–– Properties and Changes Have students work in groups as they play the videoquiz game to review key chapter concepts.
Portfolio Options Review the portfolio options that are provided throughout the chapter. Encourage students to select one product that demonstrates their best work for the chapter. Have students explain what they have learned
and why they chose this example for placement into their portfolios. Additional portfolio options may be found in the Challenge Problems booklet of the Teacher Classroom Resources. L2 P
LS
Pages 80–81 3(B), 3(C), 4(A), 4(C), 4(D), 5(A), 11(A)
81
CHAPTER CHAPTER
CHAPTER ASSESSMENT
3 ##
3
ASSESSMENT ASSESSMENT 37. Classify each of the following as a physical property
or a chemical property. (3.1)
All Chapter Assessment questions and answers have been validated for accuracy and suitability by The Princeton Review.
Go to the Chemistry Web site at science.glencoe.com or use the Chemistry CD-ROM for additional Chapter 3 Assessment.
Concept Mapping
Concept Mapping
map: state, physical properties, virtually incompressible, solid, gas, liquid, tightly packed particles, compressible, incompressible, particles far apart, loosely packed particles.
34. 35.
36. 37. 38.
39.
82
39. Classify each of the followa. b. c. d. e.
2. 3.
4.
5.
6.
7.
8.
9.
10.
11.
breaking a pencil in two water freezing and forming ice frying an egg burning wood leaves turning color in the fall
40. Is a change in phase a physical change or a chemical
change? Explain. (3.2) 41. List four indicators that a chemical change has proba-
bly taken place. (3.2)
32. Answers will vary. Water,
33.
into a bowl. Describe the changes that occur in the milk’s shape and volume. (3.1) ing as a physical change or a chemical change. (3.2)
1.
Mastering Concepts salt, and sugar are all substances. Each is a substance because it has a unique and unchanging composition. Answers will vary. Tap water is colorless, a liquid, freezes at approximately 0°C, and boils at approximately 100°C. a. intensive c. intensive b. extensive d. extensive The statement is false. Properties are affected by changes in temperature, pressure. Specific examples will vary. a. liquid d. gas b. gas e. solid c. solid f. solid a. physical d. physical b. physical e. chemical c. chemical f. physical The volume of the milk remains unchanged. Milk, which is a liquid, conforms to the shape of its container, thus the shape of the milk changes as it is poured from the carton into the bowl. a. physical d. chemical b. physical e. chemical c. chemical
aluminum has a silvery color gold has a density of 19 g/cm3 sodium ignites when dropped in water water boils at 100°C silver tarnishes mercury is a liquid at room temperature
38. A carton of milk is poured
31. Organize the following terms into a logical concept
31. 1. physical properties; 2. state; 3. solid; 4. liquid; 5. gas; 6. tightly packed particles; 7. loosely packed particles; 8. particles far apart; 9. incompressible; 10. virtually incompressible; 11. compressible
a. b. c. d. e. f.
42. Iron and oxygen combine to form iron oxide (rust).
List the reactants and products of this reaction. (3.2) 43. Use Table
Mastering Concepts 32. List three examples of substances. Explain why each
is a substance. (3.1) 33. List at least three physical properties of tap water. (3.1) 34. Identify each of the following as an extensive or inten-
sive physical property. (3.1) a. b. c. d.
melting point mass density length
35. “Properties are not affected by changes in temperature
and pressure.” Is this statement true or false? Explain. (3.1) 36. Classify each of the following as either solid, liquid,
or gas at room temperature. (3.1) a. b. c. d. e. f.
82
milk air copper helium diamond candle wax
3-1 to identify a substance that undergoes a phase change as its temperature increases from 250°C to 210°C. What phase change takes place? (3.2)
44. After burning for three hours, a
candle has lost half of its mass. Explain why this example does not violate the law of conservation of mass. (3.2) 45. Describe the difference between a
physical change and a chemical change. (3.2) 46. Describe the characteristics of a
mixture. (3.3) 47. Describe a method that could be used to separate each
of the following mixtures. (3.3) a. b. c. d.
iron filings and sand sand and salt the components of ink helium and oxygen gases
48. “A mixture is the chemical bonding of two or more
substances in any proportion.” Is this statement true or false. Explain.
Chapter 3 Matter—Properties and Changes
40. A change in phase is a physical change because the composition of the substance is not altered. 41. Probable indicators of a chemical reaction include a change in color, odor, or temperature, and/or the production of a gas or a solid upon mixing. 42. Iron and oxygen are the reactants, while iron oxide is the product formed. Iron oxygen → iron oxide
Resource Manager Chapter Assessment, pp. 13–18 L2 Supplemental Problems, Ch. 3 TestCheck Software MindJogger Videoquizzes Solutions Manual, Ch. 3 Chemistry Interactive CD-ROM, Ch. 3 quiz Reviewing Chemistry: Mastering P the TEKS, Ch. 3
CHAPTER 3 ASSESSMENT CHAPTER 3 ASSESSMENT 49. Which of the following are the same and which are
different? (3.3) a. b. c. d.
a substance and a pure substance a heterogeneous mixture and a solution a substance and a mixture a homogeneous mixture and a solution
50. Describe how a homogeneous mixture differs from a
heterogeneous mixture. (3.3) 51. A chemistry professor has developed a laboratory task
to give her students practical experience using basic separation techniques. She prepares a liquid solution of water and another compound. Assuming you are a student in the class, name the technique you would use to separate and identify the components. Give specific details of the method. 52. State the definition of an element. (3.4) 53. Name the elements contained in the following
62. A substance breaks down into its component elements
63. A 13.0-g sample of X combines with a 34.0-g sample
of Y to form the compound XY2. What is the mass of the reactants? sodium metal and chlorine gas. If 45.98 g of sodium combines with an excess of chlorine gas to form 116.89 g sodium chloride, what mass of chlorine gas is used in the reaction? 65. Copper sulfide is formed when copper and sulfur are
Law of Definite Proportions (3.4) 66. A 25.3-g sample of an unknown compound contains
55. What was Dmitri Mendeleev’s major contribution to
the field of chemistry? (3.4) 56. Is it possible to distinguish between an element and a
compound? Explain. (3.4) 57. How are the properties of a compound related to those
of the elements that comprise it? (3.4) 58. How are the elements contained within a group on the
periodic table related? (3.4) 59. Which law states that a compound always contains the
same elements in the same proportion by mass? (3.4)
Mastering Problems Properties of Matter (3.1) 60. A scientist is given the task of identifying an unknown
compound on the basis of its physical properties. The substance is a white solid at room temperature. Attempts to determine its boiling point were unsuccessful. Using Table 3-1, name the unknown compound.
45.
heated together. In this reaction, 127 g of copper reacts with 41 g of sulfur. After the reaction is complete, 9 g of sulfur remains unreacted. What is the mass of copper sulfide formed?
a. sodium chloride (NaCl) c. ethanol (C2H6O) b. ammonia (NH3) d. bromine (Br2)
Earth? Approximately how many synthetic elements have been identified? (3.4)
44.
64. Sodium chloride can be formed by the reaction of
compounds. (3.4)
54. How many naturally occurring elements are found on
43. Oxygen undergoes a phase
when it is heated. If 68.0 grams of the substance is present before it is heated, what is the combined mass of the component elements after heating?
46.
0.8 g of oxygen. What is the percent by mass of oxygen in the compound? 67. Magnesium combines with oxygen to form magne-
sium oxide. If 18.06 g of magnesium reacts completely with 6.96 g of oxygen, what is the percent by mass of oxygen in magnesium oxide? 68. When mercury oxide is heated, it decomposes into
mercury and oxygen. If 28.4 g of mercury oxide decomposes, producing 2.0 g oxygen, what is the percent by mass of mercury in mercury oxide?
47.
Law of Multiple Proportions (3.4) 69. Carbon reacts with oxygen to form two different com-
pounds. Compound I contains 4.82 g carbon for every 6.44 g of oxygen. Compound II contains 20.13 g carbon for every 53.7 g of oxygen. What is the ratio of carbon to a fixed mass of oxygen for the two compounds?
Mixed Review Sharpen your problem-solving skills by answering the following. 70. Which state of matter is the most compressible? The
least? Explain why.
Conservation of Mass (3.2) 61. A 28.0-g sample of nitrogen gas combines completely
with 6.0 g of hydrogen gas to form ammonia. What is the mass of ammonia formed? Solid
Liquid
Gas
48. Assessment
49. a. same c. different b. different d. same 50. Homogeneous mixtures contain a single phase. Heterogeneous mixtures may have many phases. 51. Using distillation, heat the solution until the boiling point of the aqueous component is reached, then note that temperature. Boil away the aqueous component and observe the remaining component. Use a table such as 3-1 or
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another resource to identify the components based on the information obtained from the distillation process. 52. An element is a substance that cannot be broken down into simpler substances by physical or chemical means. 53. a. sodium and chlorine b. nitrogen and hydrogen c. carbon, hydrogen, and oxygen d. bromine
change as its temperature increases from 250°C to 210°C. Solid oxygen melts to form liquid oxygen at a temperature of 218°C. The mass of the candle is conserved if you consider the gaseous products from the reaction. A physical change alters a substance without changing its composition, while a chemical change involves a change in composition. Mixtures are a physical blend of two or more substances in any proportion. Mixtures do not have a constant composition. The properties of the mixture are largely those of its component substances. a. A magnet can be used to draw the iron filings from the sand. b. Add water to the mixture to dissolve the salt. Filter the mixture to remove the sand, and then boil off the water so only the salt remains. c. Paper chromatography should be used to separate the components of the ink. If enough ink is available, distillation may also be used, but is far more complicated than chromatography. d. Cool the gas mixture until it condenses, then distill the condensate. The statement is false because mixtures are a physical blend of substances, not a chemical bonding of substances.
Pages 82–83 2(C), 4(A), 4(B), 4(C), 4(D), 5(A), 6(C), 11(A)
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CHAPTER CHAPTER 3 ASSESSMENT
55. 56.
57.
58.
59.
occurring elements. There are more than 20 synthetically produced elements. Mendeleev developed the first widely accepted periodic table of elements. Yes, elements can be distinguished from compounds. Compounds can be broken down into their component elements, whereas elements cannot be broken down into simpler substances. The properties of a compound are unique to that compound and different from those of its component elements. Elements within a group of the periodic table have similar chemical and physical properties. the law of definite proportions
71. Classify each of the following as a homogeneous mix-
ture or a heterogeneous mixture. (3.3) a. b. c. d.
72. Phosphorus combines with hydrogen to form phos-
phine. In this reaction, 123.9 g of phosphorus combines with excess hydrogen to produce 129.9 g of phosphine. After the reaction, 310 g of hydrogen remains unreacted. What mass of hydrogen is used in the reaction? What was the initial mass of hydrogen before the reaction? 73. A sample of a certain lead compound contains 6.46
grams of lead for each gram of oxygen. A second sample has a mass of 68.54 g and contains 28.76 g of oxygen. Are the two samples the same?
Thinking Critically 74. Applying Concepts
Air is a mixture of many gases, primarily nitrogen, oxygen, and argon. Could distillation be used to separate air into its component gases? Explain.
75. Interpreting Data
A compound contains elements X and Y. Four samples with different masses were analyzed, and the masses of X and Y in each sample were plotted on a graph. The samples are labeled I, II, III, and IV. 40
Mastering Problems Complete solutions to Chapter Assessment problems can be found in the Solutions Manual.
Law of Definite Proportions (3.4) Level 1 66. Mass percentageoxygen 3%
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III
Writing in Chemistry 76. Select a synthetic element and prepare a short written
report on its development. Be sure to cover recent discoveries, list major research centers that conduct this type of research, and describe the properties of the synthesized element. 77. Research the life of a scientist, other than Mendeleev,
who contributed to the development of the modern periodic table of elements. Write a brief biography of this person and detail his or her scientific accomplishments. 78. The results and interpretations of chemistry experi-
ments and studies are recorded and published in literally hundreds of scientific journals around the world. Visit the local library and look at several of the articles in a chemistry journal such as The Journal of the American Chemical Society. Write a brief summary of your observations regarding the format and style of writing in chemistry.
Cumulative Review Refresh your understanding of previous chapters by answering the following. 79. What is chemistry? (Chapter 1) 80. What is mass? Weight? (Chapter 1) 81. Express the following in scientific notation.
(Chapter 2) a. 34 500 b. 2665 c. 0.9640
d. e. f.
789 75 600 0.002 189
82. Perform the following operations. (Chapter 2)
20 IV
0
II
I 2
4 6 8 Mass of Y (g)
a. 107 103 b. (1.4 103) (5.1 105) c. (2 103) (4 105) 83. Convert 65°C to Kelvins. (Chapter 2) 84. Graph the following data. What is the slope of the
line? (Chapter 2) a. Which samples are from the same compound? How
compounds that are white solids, but it is sucrose that decomposes before a boiling point is determined. Therefore the unknown substance is sucrose.
Level 2 64. Masschlorine 70.91 g 65. Masscopper sulfide 159 g
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10
Properties of Matter (3.1) Level 1 60. Table 3-1 shows two
Conservation of Mass (3.2) Level 1 61. Massammonia 34.0 g 62. 68.0 g 63. 47.0 g
brass (an alloy of zinc and copper) a salad blood powder drink mix dissolved in water
Mass of X (g)
54. There are 91 naturally
ASSESSMENT
3
do you know? b. What is the approximate ratio of mass X to mass Y
in the samples that are from the same compound? c. What is the approximate ratio of mass X to mass Y
in the sample(s) that are not from the same compound?
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Energy Released by Carbon Mass (g)
Energy released (kJ)
1.00
33
2.00
66
3.00
99
4.00
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Chapter 3 Matter—Properties and Changes
67. Mass percentageoxygen 27.8% 68. Mass percentagemercury 93.0% Law of Multiple Proportions (3.4) Level 2 69. The ratio of carbon to a fixed mass of oxygen in compound I is 0.748:1, while in compound II it is 0.375:1.
Mixed Review 70. Gases are the most compressible state of matter, solids the least. Compressibility is determined by the amount of space between particles in each state. Gases have the greatest amount of space between particles, solids the least.
STANDARDIZED TEST PRACTICE CHAPTER 3
CHAPTER 3 ASSESSMENT
Use these questions and the test-taking tip to prepare for your standardized test. Interpreting Tables Use the table to answer questions 1 and 2. Mass Analysis of Two Chlorine–Fluorine Compound Samples Sample Mass chlorine (g)
Mass fluorine (g)
%Cl 65.11
I
13.022
6.978
II
5.753
9.248
?
%F 34.89 ?
1. What are the values for %Cl and %F, respectively, for
Sample II? a. b. c. d.
0.622 and 61.65 61.65 and 38.35 38.35 and 0.622 38.35 and 61.65
2. Which of the following statements best describes the
relationship between the two samples? a. The compound in Sample I is the same as in Sample
II. Therefore, the mass ratio of Cl to F in both samples will obey the law of definite proportions. b. The compound in Sample I is the same as in Sample II. Therefore, the mass ratio of Cl to F in both samples will obey the law of multiple proportions. c. The compound in Sample I is not the same as in Sample II. Therefore, the mass ratio of Cl to F in both samples will obey the law of proportions. d. The compound in Sample I is not the same as in Sample II. Therefore, the mass ratio of Cl to F in both samples will obey the law of multiple proportions. 3. After elements A and B react to completion in a closed
container, the ratio of masses of A and B in the container will be the same as before the reaction. This is true because of the law of _____ . a. b. c. d.
a. b. c. d.
it is hard and rigid it can be compressed into a smaller volume it takes the shape of its container its matter particles are close together
6. Na, K, Li, and Cs all share very similar chemical
properties. In the periodic table of elements, they most likely belong to the same _____ . a. row b. period
c. group d. element
7. A heterogeneous mixture _______ a. b. c. d.
cannot be separated by physical means. is composed of distinct areas of composition. is also called a solution. has the same composition throughout.
8. The percent by mass of sulfur in sulfuric acid, H2SO4,
is _____ . a. 32.69% b. 64.13%
sugar (sucrose) EXCEPT _____ . forms solid crystals at room temperature appears as crystals white in color breaks down into carbon and water vapor when heated tastes sweet
magnesium oxide. All of the following are true of this reaction EXCEPT _______ . a. The mass of magnesium oxide produced equals the
mass of magnesium consumed plus the mass of oxygen consumed. b. The reaction describes the formation of a new substance. c. The product of the reaction, magnesium oxide, is a chemical compound. d. Magnesium oxide has physical and chemical properties similar to both oxygen and magnesium. 10. Which of the following is NOT a chemical reaction?
dissolution of sodium chloride in water combustion of gasoline fading of wallpaper by sunlight curdling of milk
When Eliminating, Cross It Out
Consider each answer choice individually and cross out choices you’ve eliminated. If you can’t write in the test booklet, use the scratch paper. List the answer choice letters on the scratch paper and cross them out there. You’ll save time and stop yourself from choosing an answer you’ve mentally eliminated.
Standardized Test Practice
the amount of gravitational pull acting on the mass of an object. It is measured on a scale. 81. a. 3.45 104 d. 7.89 102 3 b. 2.665 10 e. 7.56 104 1 c. 9.640 10 f. 2.189 103 10 82. a. 10 b. 7.1 108 c. 8 102
Masslead/Massoxygen 6.46 Sample II: Masslead/Massoxygen 1.381 The two samples are not the same because the two Masslead/Massoxygen ratios are not the same.
74. If the mixture of gases is
9. Magnesium reacts explosively with oxygen to form
a. b. c. d.
Initial masshydrogen 316 g
73. Sample I:
Thinking Critically
c. 16.31% d. 48.57%
definite proportions multiple proportions conservation of mass conservation of energy
4. All of the following are physical properties of table a. b. c. d.
71. a. homogeneous b. heterogeneous c. heterogeneous d. homogeneous 72. Masshydrogen 6.0 g
5. A substance is said to be in the solid state if _____ .
cooled sufficiently, it will condense into a mixture of liquids. This mixture could then be distilled. 75. a. Samples I, III, and IV are the same compound. A straight line can be drawn through these three plotted points. The slope of the line is equivalent to ratio MassX/MassY. The fact that all three points are on the same line shows that they all have the same mass ratio of X to Y and must be the same compound. b. Mass ratio of X to Y for samples I, II, and IV is 3.75:1. c. Sample II mass ratio is 1.9:1
Cumulative Review 79. Chemistry is the study of
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83. 338 K 84. Slope 33 kJ/g
matter and the changes that it undergoes. 80. Mass is the measure of the amount of matter an object contains. It is measured on a balance. The weight of an object is
Standardized Test Practice 1. d 2. d
3. c 4. c
5. a 6. c
7. b 8. a
9. d 10. a Pages 84–85 2(C), 3(E), 4(A), 4(C), 4(D), 5(A), 6(C)
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