INSTRUCTOR SOLUTIONS

INSTRUCTOR SOLUTIONS

MANUAL

for

Chemistry: A Molecular Approach

Fourth Canadian Edition Nivaldo J. Tro Travis D. Fridgen Lawton E. Shaw NOTE: For Complete File, Download link at the end of this File 1 / 4

1 Copyright © 2023 Pearson Canada Inc.Review Questions 1.1 The main goal of chemistry is to seek to understand the behaviour of matter by studying the behaviour of atoms and molecules.

1.2 In solid matter, atoms or molecules pack close to each other in fixed locations. Although the atoms and molecules in a solid vibrate, they do not move around or past each other. Conse- quently, a solid has a fixed volume and rigid shape.In liquid matter, atoms or molecules pack about as closely as they do in solid matter, but they are free to move relative to each other, giving liquids a fixed volume but not a fixed shape. Liquids assume the shape of their container.In gaseous matter, atoms or molecules have a lot of space between them and are free to move relative to one another, making gases compressible. Gases always assume the shape and volume of their container.

1.3 A physical property is one that a substance displays without changing its composition, whereas a chemical property is one that a substance displays only by changing its composi- tion via a chemical change.

1.4 Changes that alter only state or appearance, but not composition, are called physical changes.The atoms or molecules that compose a substance do not change their identity during a physical change. For example, when water boils, it changes its state from a liquid to a gas, but the gas remains composed of water molecules, so this is a physical change. When sugar dissolves in water, the sugar molecules are separated from each other, but the molecules of sugar and water remain intact.In contrast, changes that alter the composition of matter are called chemical changes. During a chemical change, atoms rearrange, transforming the original substances into different sub- stances. For example, the rusting of iron, the combustion of natural gas to form carbon diox- ide and water, and the denaturing of proteins when an egg is cooked are examples of chemical changes.

1.5 In chemical and physical changes, matter often exchanges energy with its surroundings. In these exchanges, the total energy is always conserved; energy is neither created nor destroyed.Systems with high potential energy tend to change in the direction of lower potential energy, releasing energy into the surroundings.

1 Units of Measurement for Physical and Chemical Change 2 / 4

• Chapter 1 Units of Measurement for Physical and Chemical Change

Copyright © 2023 Pearson Canada Inc.

1.6 Chemical energy is potential energy. It is the energy that is contained in the bonds that hold the molecules together. This energy arises primarily from electrostatic forces between the electrically charged particles (protons and electrons) that compose atoms and molecules. Some of these arrangements—such as the one within the molecules that compose gasoline—have a much higher potential energy than others. When gasoline undergoes combustion the arrangement of these particles changes, creating molecules with much lower potential energy and transferring a great deal of energy (mostly in the form of heat) to the surround- ings. A raised weight has a certain amount of potential energy (dependent on the height the weight is raised) that can be converted to kinetic energy when the weight is released.

1.7 The SI base units include the metre (m) for length, the kilogram (kg) for mass, the second (s) for time, and the Kelvin (K) for temperature.

1.8 The two different temperature scales are Kelvin (K) and Celsius (°C). The size of the degree is the same in the Kelvin and the Celsius scales.

1.9 Prefix multipliers are used with the standard units of measurement to change the value of the unit by powers of 10.For example, the kilometre has the prefix “kilo,” meaning 1000 or 10 3

. Therefore:

• kilometre = 1000 metres = 10

3 metres Similarly, the millimetre has the prefix “milli,” meaning 0.001 or 10 −3 .

• millimetre = 0.001 metres = 10

−3 metres 1.10 A derived unit is a combination of other units. Examples of derived units include speed in metres per second (m s −1 ), volume in metres cubed (m 3 ), and density in grams per cubic centimetre (g cm −3 ).

1.11 The density (d) of a substance is the ratio of its mass (m) to its volume (V): Mass Density = or = Volume m d V

The density of a substance is an example of an intensive property, one that is independent of the amount of the substance. Mass is one of the properties used to calculate the density of a substance.Mass, in contrast, is an extensive property, one that depends on the amount of the substance.

1.12 An intensive property is a property that is independent of the amount of the substance. An extensive property is a property that depends on the amount of the substance.

1.13 Measured quantities are reported so that the number of digits reflects the uncertainty in the measure- ment. The nonplaceholding digits in a reported number are called significant figures.

1.14 In multiplication or division, the result carries the same number of significant figures as the measure- ment with the fewest significant figures.

1.15 In addition or subtraction, the result carries the same number of decimal places as the quantity with the fewest decimal places.

1.16 When taking a logarithm, the number of decimal places (the mantissa) is determined by the number of the significant figures in the number whose logarithm is being calculated. The number before the deci- mal place is the magnitude of the logarithm. For example, log10 (103.55) = 2.01515 1.17 When taking an antilogarithm of a number, the mantissa of the number whose antilogarithm is being calculated determines the final significant figures in the answer. For example, 10 1.236

= 17.2

1.18 Accuracy refers to how close the measured value is to the actual value. Precision refers to how close a series of measurements are to one another or how reproducible they are. A series of measurements can be precise (close to one another in value and reproducible) but not accurate (not close to the true value).

1.19 Random error is error that has equal probability of being too high or too low. Almost all measurements have some degree of random error. Random error can, with enough trials, average itself out. Systematic error is error that tends toward being either too high or too low. Systematic error does not average out with repeated trials. 3 / 4

Chapter 1 Units of Measurement for Physical and Chemical Change 3 Copyright © 2023 Pearson Canada Inc.

1.20 Using units as a guide to solving problems is often called dimensional analysis. Units should always be included in calculations; they are multiplied, divided, and cancelled like any other algebraic quantity.Problems by Topic 1.21 (a) chemical property (burning involves breaking and making bonds, so bonds must be broken and made to observe this property) (b) physical property (shininess is a physical property and so can be observed without making or breaking chemical bonds) (c) physical property (odour can be observed without making or breaking chemical bonds) (d) chemical property (burning involves breaking and making bonds, so bonds must be broken and made to observe this property) 1.22 (a) physical property (vaporization is a phase change and so can be observed without making or breaking chemical bonds) (b) physical property (sublimation is a phase change and so can be observed without making or breaking chemical bonds) (c) chemical property (rusting involves the reaction of iron with oxygen to form iron oxide; observ- ing this process involves making and breaking chemical bonds) (d) physical property (colour can be observed without making or breaking chemical bonds) 1.23 (a) chemical change (new compounds are formed as methane and oxygen react to form carbon diox- ide and water) (b) physical change (vaporization is a phase change and does not involve the making or breaking of chemical bonds) (c) chemical change (new compounds are formed as propane and oxygen react to form carbon dioxide and water) (d) chemical change (new compounds are formed as the metal in the frame is converted to oxides) 1.24 (a) chemical change (new compounds are formed as the sugar burns) (b) physical change (dissolution is a phase change and does not involve the making or breaking of chemical bonds) (c) physical change (this is simply the rearrangement of the atoms) (d) chemical change (new compounds are formed as the silver converts to an oxide) 1.25 (a) physical change (vaporization is a phase change and does not involve the making or breaking of chemical bonds) (b) chemical change (new compounds are formed) (c) physical change (vaporization is a phase change and does not involve the making or breaking of chemical bonds) 1.26 (a) physical change (vaporization of butane is a phase change and does not involve changing its chemical composition) (b) chemical change (new compounds are formed as the butane combusts) (c) physical change (vaporization of water is a phase change and does not involve changing its chem- ical composition)

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