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Solution Manual For Chemistry: An Atoms-Focused Approach, 3rd Edition

Solution Manual For Chemistry: An Atoms-Focused Approach, 3rd Edition helps you retain textbook concepts through organized explanations.

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    i SOLUTIONS MANUAL Chemistry: An Atoms-Focused Approach Third Edition

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    iv Contents Preface Chapter 1 | Matter and Energy: An Atomic Perspective Chapter 2 | Atoms, Ions, and Molecules: The Building Blocks of Matter Chapter 3 | Atomic Structure: Explaining the Properties of Elements Chapter 4 | Chemical Bonding: Understanding Climate Change Chapter 5 | Bonding Theories: Explaining Molecular Geometry Chapter 6 | Intermolecular Forces: Attractions between Particles Chapter 7 | Stoichiometry: Mass Relationships and Chemical Reactions Chapter 8 | Reaction in Aqueous Solutions: Chemistry of the Hydrosphere Chapter 9 | Properties of Gases: The Air We Breathe Chapter 10 | Thermochemistry: Energy Changes in Chemical Reactions Chapter 11 | Properties of Solutions: Their Concentrations and Colligative Properties Chapter 12 | Thermodynamics: Why Chemical Reactions Happen Chapter 13 | Chemical Kinetics: Clearing the Air Chapter 14 | Chemical Equilibrium: Equal but Opposite Reaction Rates Chapter 15 | Acid–Base Equilibria: Proton Transfer in Biological Systems Chapter 16 | Additional Aqueous Equilibria: Chemistry and the Oceans Chapter 17 | Electrochemistry: The Quest for Clean Energy Chapter 18 | The Solid State: A Particulate View Chapter 19 | Organic Chemistry: Fuels, Pharmaceuticals, and Modern Materials Chapter 20 | Biochemistry: The Compounds of Life Chapter 21 | Nuclear Chemistry: The Risks and Benefits Chapter 22 | Main Group Elements: Life and the Periodic Table Chapter 23 | Transition Metals: Biological and Medical Applications Problem Correlation Table (Second to Third Edition)

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    1 CHAPTER 1 | Matter and Energy: An Atomic Perspective 1.1. Collect and Organize Figure P1.1(a) shows “molecules,” each consisting of one red sphere and one blue sphere, and Figure P1.1(b) shows separate blue spheres and red spheres. For each image we are to identify the class of matter. We need to determine whether the substance(s) depicted is/are solid, liquid, or gas and whether the images show an element, a compound, or a mixture that is homogeneous or heterogeneous. Analyze An element is composed of all the same type of atom, and a compound is composed of two or more types of atoms. Solids have a definite volume and a highly ordered arrangement where the particles are close together. Liquids also have a definite volume but have a disordered arrangement of particles that are close together. Gases have disordered particles that fill the volume of the container and are far apart from each other. Homogeneous mixtures have a uniform distribution and composition, and heterogeneous mixtures contain regions of different composition. Solve (a) Because each particle in Figure P1.1(a) consists of one red sphere and one blue sphere, all the particles are the same—that is a compound. The particles fill the container and are disordered, so those particles are in the gas phase. (b) Because it shows a mixture of red and blue spheres, Figure P1.1(b) depicts a mixture of blue elemental atoms and red elemental atoms. The blue spheres fill the container and are disordered, so those particles are in the gas phase. The red spheres have a definite volume and are ordered, so those particles are in the solid phase. This is a heterogeneous mixture. Think About It Remember that both elements and compounds may be either pure or present in a mixture. 1.2. Collect and Organize Figure P1.2(a) shows “atoms” of only red spheres, and Figure P1.2(b) has “molecules” consisting of two red spheres or two blue spheres. For each image we are to identify the class of matter. We need to determine whether the substance(s) depicted is/are solid, liquid, or gas and whether the images show an element, a compound, or a mixture that is homogeneous or heterogeneous. Analyze A pure substance (whether element or compound) is composed of all the same type of molecule or atom, not a mixture of two kinds. An element is composed of all the same type of atom, and a compound is composed of two or more types of atoms. Solids have a definite volume and a highly ordered arrangement where the particles are close together. Liquids also have a definite volume but have a disordered arrangement of particles that are close together. Gases have disordered particles that fill the volume of the container and are far apart from each other. Homogeneous mixtures have a uniform distribution and composition, and heterogenous mixtures contain regions of different composition. Solve (a) Because all the atoms are of the same type, Figure P1.2(a) depicts a pure element. The particles take up a definite volume and are ordered, so that element is in the solid phase. (b) Because it shows a mixture of blue diatomic molecules and red diatomic molecules, Figure P1.2(b) depicts a mixture of two elements. Both the blue and red diatomic particles fill the container’s volume and are highly disordered; the mixture depicted is in the gas phase. This is a homogeneous mixture. Think About It Elements do not need to be present as single atoms. They may be diatomic, as in H 2 or Br 2 , or even more highly associated, as in S 8 or P 4 .

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    2 | Chapter 1 1.3. Collect and Organize In this question we are to consider whether the reactants, as depicted, undergo a chemical reaction and/or a phase change. Analyze Chemical reactions involve the breaking and making of bonds in which atoms are combined differently in the products than in the reactants. When we consider a possible phase change, remember the following: Solids have a definite volume and a highly ordered arrangement where the particles are close together. Liquids also have a definite volume but have a disordered arrangement of particles that are close together. Gases have disordered particles that fill the volume of the container and are far apart from one another. Solve In Figure P1.3, two pure diatomic elements (red–red and blue–blue) in the gas phase recombine to form a compound (red–blue) in the solid phase (ordered array of molecules). Therefore, answer b describes the reaction shown. Think About It A phase change does not necessarily accompany a chemical reaction. We will learn later that the polarity of the product will determine whether a substance will be in the solid, liquid, or gaseous state at a given temperature. 1.4. Collect and Organize In this question we are to consider whether the reactants, as depicted, undergo a chemical reaction (either recombination or decomposition) and/or a phase change. Analyze Chemical reactions involve the breaking and making of bonds in which atoms are combined differently in the products from how they are combined in the reactants. When we consider a possible phase change, remember the following: Solids have a definite volume and a highly ordered arrangement where the particles are close together. Liquids also have a definite volume but have a disordered arrangement of particles that are close together. Gases have disordered particles that fill the volume of the container and are far apart from one another. Solve In Figure P1.4 we see that no recombination of the diatomic molecules occurs. One pure diatomic element (red– red) condenses to a slightly disordered phase, whereas the other diatomic element (blue–blue) remains in the gas phase. Therefore, answer a describes the reaction pictured. Think About It Cooling of air to different temperatures in a controlled fashion separates the components of air. 1.5. Collect and Organize From the diagram showing gaseous CO 2 at room temperature, we are to describe what the particulate image would be after cooling this gas to 180 K. Analyze Looking up the information on the internet for carbon dioxide, CO 2 ( g ), we find that it has a sublimation temperature of –78 ° C or 195 K. This temperature is higher than 180 K. Therefore, CO 2 at 180 K will be in the solid phase. Solve The particulate image of CO 2 at 180 K will show the linear CO 2 molecules condensed at the bottom of the box on the right with the molecules touching and forming a regular pattern. Think About It Solid CO 2 is also known as dry ice, and at normal pressure (1 atm) the only phase change we observe is sublimation, not melting or boiling.

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    Matter and Energy | 3 1.6. Collect and Organize From the diagram showing a mixture of gaseous diatomic substances, we are to describe what the particulate image would be after cooling this mixture from 298 K to 70 K. Analyze Using the atomic color palette on the inside back cover of the textbook, we can identify these three gases as hydrogen (white, H 2 ), nitrogen (blue, N 2 ), and oxygen (red, O 2 ). From Appendix 3.2 we obtain the melting point and boiling point for each of these gases: hydrogen (mp = –259.14 ° C, bp = –252.87 ° C), nitrogen (mp = –210.00 ° C, bp = –195.8 ° C), oxygen (mp = –218.8 ° C, bp = –182.95 ° C). We can then compare these to the temperature to which we are cooling the mixture, 70 K, which we can convert to kelvin through the following equation: ( T )° C = T (K) – 273.15 or ( T )° C = 70 – 273.15 = –203 ° C Solve Because 70 K or –203 ° C is higher than both the melting point and the boiling point of hydrogen, it is in the gas phase; the white diatomic molecules in the particulate picture will remain far apart and will be scattered in the volume of the box. Because 70 K or –203 ° C is between the melting point and the boiling point of both nitrogen and oxygen, N 2 and O 2 will be in the liquid phase; the blue and red diatomic molecules in the particulate picture will be condensed at the bottom of the box, but will not be lined up in any regular pattern, signifying that they are in the liquid state. Think About It At a temperature of, for example, –215 ° C or 58 K, the three gases will be in three different phases; hydrogen in the gas phase, oxygen in the liquid phase, and nitrogen in the solid phase. 1.7. Collect and Organize Using the atomic color palette on the inside back cover of the textbook, we can identify these atoms in these molecules. Chemical formulas describe the type and number of atoms in a molecule. Analyze The color palette identifies white atoms as hydrogen, red atoms as oxygen, black atoms as carbon, and green atoms as chlorine. To determine the chemical formula, we indicate the number of each type of atom as a subscript. Solve (a) CH 2 O (b) C 2 H 6 O 2 (c) CCl 4 Think About It For carbon-containing compounds, it is standard form to list the atoms in the following order: C, H, N, O. 1.8. Collect and Organize Using the atomic color palette on the inside back cover of the textbook, we can identify these atoms in these molecules. Chemical formulas describe the type and number of atoms in a molecule. Analyze The color palette identifies white atoms as hydrogen, red atoms as oxygen, and black atoms as carbon. To determine the chemical formula, we indicate the number of each type of atom as a subscript. Solve (a) C 3 H 8 O (b) C 4 H 10 O (c) C 4 H 8 O

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    4 | Chapter 1 Think About It For these carbon-containing compounds, it is standard form to list the atoms in the following order: C, H, O. 1.9. Collect and Organize Given that the pill manufactured by a pharmaceutical company is to weigh 3.25 mg, we are asked to compare the precision and accuracy of the data in the two graphs of masses of 4 pills. Analyze Precision in these pill samples means that the four pills have masses that do not vary much; accuracy in these pill samples means that the four pills, on average, have a mass that is close to the desired mass of 3.25 mg. Solve The graph for Sample A shows values that vary, but that are close to the desired value of 3.25 mg—this sample is accurate but not precise . The graph for Sample B shows values that do not vary much, none of which is close to the desired value of 3.25 mg—this sample is precise but not accurate . Think About It A sample that was both precise and accurate would show all four pills close in value to each other and all very close to the desired mass of 3.25 mg. 1.10. Collect and Organize From the representations [A] through [I] in Figure P1.10, we are to choose the one that contains the most atoms, contains the most elements, shows a solid solution, shows a homogeneous mixture, shows a compound, or shows an element. Analyze To categorize the representations, we need to apply the definitions of atom, element, solid solution, homogeneous mixture, pure compound, and pure element. An atom is the smallest particle constituent that makes up matter; an element is a substance composed of only one type of atom; a solid solution is a mixture of two or more substances that form a homogeneous solid; a homogeneous mixture is a mixture of elements or compounds that has uniform composition and properties; a pure compound is a substance made of different elements in a specific ratio; a pure element is a substance made up of only one kind of atom with no other elements present in the substance. Solve (a) Of the representations, only [B], [F], [G], and [H] are molecules. Of those [B], glycine, contains 10 atoms; [F], ammonia, contains 4 atoms; [G], hydrogen peroxide, contains 4 atoms; and [H], propane, contains 11 atoms. Therefore, [H], propane, contains the most atoms. (b) Of the representations, [B], [F], [G], and [H] are molecular representations of compounds. Of those [B], glycine, contains 4 elements (C, H, N, and O); [F], ammonia, contains 2 elements (N and H); [G], hydrogen peroxide, contains 2 elements (H and O); and [H], propane, contains 2 elements (C and H). Therefore, [B], glycine, contains the most elements. (c) [A], brass is a solid solution composed of copper and zinc. (d) [E] saline (dissolved NaCl in water) and [A] brass (a solid solution of copper and zinc) are homogeneous mixtures that have uniform composition and properties. (e) The pure substances in the list that are compounds are: [B] (glycine), [F] (ammonia), [G] (hydrogen peroxide), and [H] (propane). (f) The pure elements in the list are: [C] (helium), [D] (mercury), and [I] (platinum). Think About It Technically, by the broad definition, brass is a homogeneous mixture. However, for mixtures of metals or other solids, we usually use the term solid solution to describe them. You might also find the term alloy used for a solid solution of metal elements. 1.11. Collect and Organize For this question we are asked to differentiate “hypothesis” from “scientific theory.”

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    Matter and Energy | 5 Analyze These terms are part of the scientific method and result from different aspects of the process of observing and explaining a natural phenomenon. Solve A hypothesis is a tentative explanation of an observation or set of observations, whereas a scientific theory is a concise explanation of a natural phenomenon that has been extensively tested and explains why certain phenomena are always observed. Think About It Notice that a hypothesis might become a theory after much experimental testing. 1.12. Collect, Organize, and Analyze In this question we consider how a hypothesis becomes a theory. Solve A theory is formed from a hypothesis when the hypothesis has been extensively tested with many observations and experiments. A theory is the best (current) possible explanation extensively supported by experimentation. Think About It A theory, tested over time, may be elevated to become a scientific law. 1.13. Collect and Organize In this question we consider how Dalton’s atomic theory supported his law of multiple proportions. Analyze Dalton’s law of multiple proportions states that when two elements combine to make two (or more) compounds, the ratio of the masses of one of the elements, which combine with a given mass of the second element, is always a ratio of small whole numbers. His atomic theory states that matter in the form of elements and compounds is made up of small, indivisible units—atoms. Solve Dalton’s atomic theory explained the small, whole-number mass ratios in his law of multiple proportions because the compounds contained small, whole-number ratios of atoms of different elements per molecule or formula unit. Think About It Dalton’s theory is not strictly true. Atoms are divisible into electrons, protons, and neutrons (and even further into subatomic quarks), and some compounds do not have whole-number ratios of atoms. For most matter and most compounds that we encounter in chemistry, though, his theory is true. 1.14. Collect and Organize In this question we are asked to explain why the existence of atoms in matter was considered a philosophy in ancient Greece but had become a theory in the early 1800s. Analyze A philosophy is a set of beliefs arrived at through rational thought and not tested by experiment. A theory is formed from a hypothesis when the hypothesis has been extensively tested with many observations and experiments. A theory is the best (current) possible explanation extensively supported by experimentation. Solve The philosophy of the atom became the atomic theory in the 1800s when much of the experimental evidence that had accumulated pointed to the particulate nature of matter. That mounting evidence changed the belief into a tested best explanation for the nature of matter.

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    6 | Chapter 1 Think About It Some materials do not conform to the law of definite or constant proportions that led to the atomic theory. An example is a nonstoichiometric compound such as Fe 0.95 O, in which the proportions of the elements composing the material can vary and the elements are not in strict whole-number proportions. 1.15. Collect and Organize In this question we are asked to explain why scientists opposed Proust’s law of definite proportions when he proposed it. Analyze The law of definite proportions states that the ratio of elements in a compound is always the same. Solve Proust’s law needed to have corroborating evidence to fully support it. At the time, experiments to prepare a compound of tin with oxygen yielded various compositions. The compounds they prepared, when analyzed later, turned out to be mixtures of two compounds of tin oxide. Think About It Tin can form either tin(II) oxide, SnO, or tin(IV) oxide, SnO 2 . What do you think the ratio of the elements would be for a 50–50 mixture of these two compounds? Of a 25–75 mixture? 1.16. Collect and Organize For this question we are asked to describe a chemical reaction that illustrates Dalton’s law of multiple proportions. Analyze Dalton’s law of multiple proportions states that when two elements combine to make two (or more) compounds, the ratio of the masses of one of the elements, which combine with a given mass of the second element, is always a ratio of small whole numbers. Solve The law of multiple proportions can be illustrated for any combination of two elements that can give two compounds. One example is the reaction of carbon with oxygen to give either carbon monoxide, CO, or carbon dioxide, CO 2 . C( s ) + ½ O 2 ( g ) ® CO( g ) C( s ) + O 2 ( g ) ® CO 2 ( g ) Think About It Other examples of this are: nitrogen reacting with oxygen to give various NO x species like NO, NO 2 , N 2 O, N 2 O 5 , and several others; and sulfur reacting with oxygen to give SO 2 , SO 3 , S 2 O, S 2 O 2 , and several others. 1.17. Collect and Organize We are to define theory as used in everyday conversation and differentiate it from its use in science. Analyze Theory in everyday conversation has a quite different meaning from its meaning in science. Solve Whereas theory in normal conversation means someone’s idea or opinion that is open to speculation, a scientific theory is a concise and testable explanation of natural phenomena based on observation and experimentation that can accurately predict the results of experiments. Think About It Theory in normal conversation is more akin to a hypothesis or a guess that may or may not be testable.

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    Matter and Energy | 7 1.18. Collect and Organize We are asked to give an example of a scientific theory that accurately predicted the results of an experiment before it was carried out. Analyze A theory is a concise and testable explanation of natural phenomena based on observation and experimentation. There are many examples in science where theory predicted the results of an experiment first. Solve Answers may vary, but you might give this as a chemistry example: Mendeleev’s formulation of the periodic table predicted the existence of elements such as gallium and germanium and predicted their physical properties such as densities, melting points, and boiling points along with their chemical reactivities. Think About It More recent examples include the prediction of the existence of gravitational waves (LIGO Lab) and the prediction of the existence and properties of the Higgs boson. 1.19. Collect and Organize We are asked to consider whether a scientific hypothesis can be disproven. Analyze A scientific hypothesis is a testable, yet tentative, explanation for an observation (or set of observations) in the natural world. Solve You can disprove a scientific hypothesis through an experiment that does not give the predicted outcome. Think About It An important feature of scientific inquiry that distinguishes it from other forms of inquiry is that the hypotheses are testable and that failure results in a reexamination of the hypotheses. 1.20. Collect and Organize We consider in this question whether a theory can be proven. Analyze In science, a theory is the best (current) possible explanation extensively supported by experimentation and observations. Solve Theory is nearly equivalent to fact in science, without being the absolute truth. A theory is hard to prove absolutely but has many, many supporting experiments whose observations strongly support it. Think About It One experiment that is counter to the explanation for a phenomenon that the theory explains could disprove a theory, so theories may be toppled and replaced with new explanations and theories. 1.21. Collect and Organize For the foods listed, we are to determine which are heterogeneous mixtures. Analyze A heterogeneous mixture has visible regions of different composition. Solve Clear regions of different composition are evident in a Snickers bar (b) and in an uncooked hamburger (d), but not in bottled water (a) or in grape juice (c).

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    8 | Chapter 1 Think About It Bottled water contains a homogeneous mixture of water and small amounts of dissolved minerals such as salts of sodium, magnesium, and calcium that give the water its flavor. 1.22. Collect and Organize For the foods listed, we are to determine which are homogeneous. Analyze Homogeneous mixtures have the same composition throughout. Solve Freshly brewed coffee and vinegar (a, b) are homogeneous mixtures. A slice of white bread and a slice of ham (c, d) are heterogeneous mixtures. Think About It A slice of white bread is considered heterogeneous because its crust is different from the interior bread, and the bread contains gas bubbles that are clearly seen as tiny holes. If the coffee contains unfiltered sediment or the vinegar contains remnants of the mother of vinegar (a cellulose disc containing acetic acid bacteria added to an alcohol to change it into vinegar), then it would be considered a heterogeneous mixture. 1.23. Collect and Organize For the foods listed, we are to determine which are heterogeneous. Analyze A heterogeneous mixture has visible regions of different composition. Solve Distinct regions of different composition are evident in orange juice (with pulp) (d) and tomato juice (e), but not in apple juice, cooking oil, or solid butter (a–c). Think About It When butter melts, you notice milk solids and clear regions that are definitely discernible. Therefore, homogeneous solid butter becomes heterogeneous when heated. 1.24. Collect and Organize For the substances listed, we are to determine which are homogeneous. Analyze Homogeneous mixtures have the same composition throughout. Solve Sweat, gasoline, and compressed air in a scuba tank (b, d, and e) are homogeneous. Think About It Nile River water (c) and a piece of wood (a) are heterogeneous because they have distinct regions that are discernible. Nile River water contains sediment and there is visible uneven distribution of heartwood and knots, for example, in a piece of wood. 1.25. Collect and Organize We are asked to consider whether distillation would be effective in removing suspended soil particles from water. Analyze In distillation, evaporation of a liquid and subsequent condensation of the vapor is used to separate substances of different volatilities.

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    Matter and Energy | 9 Solve Soil particles are not volatile, but water is; we can boil water, but not the soil. Therefore, yes, distillation can be used to remove soil particles from water. It is not a widely used process to purify water because boiling water is energy- and time-intensive. Filtration would be both cheaper and faster than distillation. Think About It In this distillation process we would collect pure water through condensation, and the soil particles would be left behind in the distillation flask. 1.26. Collect and Organize Referring to Figure 1.8(b) in the textbook, we are to decide which compounds interact more strongly with the stationary phase on the basis of their relative positions as the liquid phase migrates up the solid phase in a chromatography experiment. Analyze In chromatography, a mixture of dissolved substances is placed on a solid stationary phase and a mobile phase (solvent) is used to separate the components. Substances that have more affinity for the stationary phase and less for the mobile phase move more slowly. Solve The yellow-colored compounds at the bottom bind more tightly with the stationary phase than the green ones or the yellow ones at the top; they did not move as far up the stationary phase with the mobile phase. Think About It Figure 1.8(b) shows just one kind of chromatography method, namely, paper chromatography on paper. Other examples include gas chromatography, ion exchange chromatography, and liquid chromatography, but they all operate on the same principle of the substances in the mixture having different affinities for the stationary and mobile phases. 1.27. Collect and Organize For this question we are to list some chemical and physical properties of gold. Analyze A chemical property is seen when a substance undergoes a chemical reaction or is resistant to reaction with another substance. A physical property can be seen without any transformation of one substance into another. Solve One chemical property of gold is its resistance to corrosion (oxidation). Gold’s physical properties include its density, color, melting temperature, and electrical and thermal conductivity. Think About It Another metal that does not corrode (or rust) is platinum. Platinum and gold, along with palladium, are often called noble metals . 1.28. Collect and Organize For this question we are to compare the physical properties of gold and silver. Analyze Physical properties include color, metallic luster, malleability, ductility, melting point, boiling point, density, electrical conductivity, and thermal conductivity. Solve Both gold and silver have metallic luster, are malleable, and conduct electricity. However, gold and silver have different densities, different melting temperatures, and different colors.

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    10 | Chapter 1 Think About It The yellow color of pure gold, compared with most metals, which are silvery, is the result of relativistic effects in the atom. 1.29. Collect and Organize We are asked in this question to name three properties to distinguish among table sugar, water, and oxygen. Analyze We can distinguish among substances by using either physical properties (such as color, melting point, and density) or chemical properties (such as chemical reactions, corrosion, and flammability). Solve We can distinguish among table sugar, water, and oxygen by examining their physical states (sugar is a solid, water is a liquid, and oxygen is a gas at normal temperatures and pressures) and by their densities, melting points, and boiling points. Think About It These three substances are also very different at the atomic level. Oxygen (O 2 ) is a pure element made up of diatomic molecules; water is a compound made up of discrete molecules composed of hydrogen and oxygen atoms (H 2 O); and table sugar is a solid compound made up of carbon, hydrogen, and oxygen atoms. 1.30. Collect and Organize We are asked in this question to name three properties to distinguish among table salt, sand, and copper. Analyze We can distinguish among substances by using either physical properties (such as color, melting point, and density) or chemical properties (such as chemical reactions, corrosion, and flammability). Solve We can distinguish among table salt, sand, and copper by examining their color (salt is composed of small cubic white crystals, sand is irregularly shaped and many-colored, and copper is a reddish metal). Salt will dissolve in water, whereas sand and copper will not. Copper conducts electricity, whereas solid table salt and sand do not. The densities of these substances also will differ. Think About It These three substances are also very different at the atomic level. Table salt is a crystalline ionic solid composed of sodium cations and chloride anions. Sand is a covalent network solid most commonly composed of silica, a compound of silicon and oxygen. Copper is a pure element and a metallic crystal. 1.31. Collect and Organize From the list of properties of sodium, we are to determine which are physical and which are chemical properties. Analyze Physical properties are those that can be observed without transforming the substance into another substance. Chemical properties are observed only when one substance reacts with another and therefore is transformed into another substance. Solve Density, melting point, thermal and electrical conductivity, and softness (a–d) are all physical properties, whereas tarnishing and reaction with water (e and f) are both chemical properties. Think About It Because the density of sodium is less than that of water, a piece of sodium will float on water as it reacts. Because sodium is more dense than kerosene, with which it does not react chemically, Na can, with great care, be stored in the lab in a container under kerosene.

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    Matter and Energy | 11 1.32. Collect and Organize From the list of properties of hydrogen gas, we are to determine which are physical and which are chemical properties. Analyze Physical properties are those that can be observed without transforming the substance into another substance. Chemical properties are observed only when one substance reacts with another and therefore is transformed into another substance. Solve Density, boiling point, and electrical conductivity (a, c, and d) are all physical properties, whereas the reaction of hydrogen with oxygen (b) is a chemical property. Think About It Because the density of hydrogen gas is lower than that of any other gas, a lightweight balloon filled with hydrogen will float in air like the more familiar helium balloon. 1.33. Collect and Organize We are to explain whether an extensive property can be used to identify a substance. Analyze An extensive property is one that, like mass, length, and volume, is determined by size or amount. Solve Extensive properties will change with the size of the sample and therefore cannot be used to identify a substance. Think About It We could, for example, have the same mass of feathers and lead, but their mass alone will not tell us which mass measurement belongs to which—the feathers or the lead. 1.34. Collect and Organize Of the properties listed, we are to choose which are intensive properties. Analyze An intensive property does not depend on the size or amount of the sample. Solve Of the properties on the list, freezing point (a) and temperature (c) are intensive properties. Heat content (b) depends on sample size and is therefore an extensive property. Think About It Intensive properties are related to chemical interactions between atoms and molecules in the substance. 1.35. Collect and Organize We are to explain whether the extinguishing of fires by carbon dioxide, CO 2 , is a result of its chemical or physical properties (or both). Analyze Physical properties are those that can be observed without transforming the substance into another substance. Chemical properties are observed only when one substance reacts with another and therefore is transformed into another substance. Solve Carbon dioxide is a nonflammable gas (a chemical property; it does not burn) and it is more dense than air (a physical property; it smothers the flames by excluding oxygen from the fuel). Therefore, CO 2 ’s fire-extinguishing properties are due to both its physical and its chemical properties.

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    12 | Chapter 1 Think About It Some metals, such as magnesium, will burn in carbon dioxide; those fires cannot be extinguished with a CO 2 fire extinguisher. 1.36. Collect and Organize We are to explain whether the resistance of stainless steel to corrosion is a result of its chemical or physical properties. Analyze Physical properties are those that can be observed without transforming the substance into another substance. Chemical properties are observed only when one substance reacts with another and therefore is transformed into another substance. Solve Corrosion is the chemical reaction of a metal with a substance such as oxygen, and so the lower reactivity of stainless steel must then derive from its chemical properties. Think About It Stainless steel contains chromium, which forms a passive layer of chromium oxide on the surface to protect the iron in the steel from contacting oxygen-containing air and then rusting. 1.37. Collect and Organize We are asked to compare the arrangement of water molecules in water as a solid (ice) and in water as a liquid. Analyze Figure A1.37 shows the arrangement of the water molecules in both those phases. Figure A1.37 Solve Water molecules in both the ice and liquid forms contain interactions that link individual molecules closely together. The arrangement of the molecules in liquid water have no long-range structure or ordering, whereas in ice the molecules are arranged in a rigid hexagonal arrangement with voids within the structure. Think About It The structure of ice is more open than the structure of liquid water. That is why, when water freezes, it expands. 1.38. Collect and Organize We are asked to describe what occupies the space between the molecules of a gas. Analyze A gas consists of particles (atoms or molecules) that are far apart from each other. Solve Nothing (no other atoms or molecules) exists in the space between particles in a gas.

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    Matter and Energy | 13 Think About It Because a gas consists of a lot of empty space, most gases are highly compressible. 1.39. Collect and Organize We are to determine which phase (solid, liquid, or gas–all of which are present at the triple point ) has the greatest particle motion and which has the least. Analyze Gases have particles much separated from each other; these particles, therefore, have a wide range of movement (more degrees of freedom). Particles in solids and liquids are close to one another, and therefore the particle motion in both phases is restricted. Solids hold their particles in rigid arrays. Solve Because of their freedom of movement, gases have the greatest particle motion; because of the restriction of their solid lattice, solids have the least particle motion. Think About It Heating a solid or liquid can melt or vaporize a substance. During these phase changes with the addition of heat, particle motion increases. 1.40. Collect and Organize We are to identify the chemical nature of the gas inside the bubbles in boiling water. Analyze Heating a substance increases the molecules’ motion. If enough heat is added, the molecules may undergo a phase change. Solve In boiling water, the liquid water is undergoing a phase change to water vapor. The bubbles are composed of gaseous water. Think About It The energy required to boil water is not enough energy to break the H—O bonds in water. Therefore, at water’s boiling point, the bubbles do not contain hydrogen and oxygen gas from the decomposition of water. Water vapor, also known as steam, is invisible; the “steam” seen around hot drinks on cold days results from droplets of liquid water that condensed as the vapor cooled.

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