Chapter 1

In the following scenario, identify which of the statements represents a theory, law, or hypothesis. (a) A student exploring the properties of gases proposes that if she decreases the volume of a sample of gas then the pressure exerted by the sample will increase. (b) Many scientists over time have conducted similar experiments and have concluded that pressure and volume are inversely proportional. (c) She proposes that the reason this occurs is that if the volume is decreased, more molecules will collide with a given area of the container walls, causing the pressure to be greater.

State whether the following is a hypothesis, theory, or law of science. Global climate change is occurring because of human-generated carbon dioxide. Explain.

What is meant by the phrase "sustainable development?

What is meant by the phrase "green chemistry"?

One of the winners of the 2016 Presidential Green Chemistry Challenge Awards was a process to generate dodecanedioic acid (DDA), a chemical used in making certain nylons. The older process uses chemicals from fossil fuels, uses nitric acid, and produces a greenhouse gas, dinitrogen monoxide. This process also requires high temperatures and pressures. The new process uses a modified yeast strain to manufacture DDA from an acid derived from palm kernel oil or coconut oil, is run near room temperature and pressure, avoids the use of nitric acid, does not generate dinitrogen monoxide, and leads to a higher purity product. Which principles of green chemistry are being followed by this new process compared to the older process?

Give the name of each of the following elements: (a) \(\mathrm{C}\) (b) K (c) \(\mathrm{Cl}\) (d)\mathbf{P} (e) \(\mathrm{Mg}\) (f) \(\mathrm{Ni}\)

Give the name of each of the following elements: (a) Mn (b) Cu (c) \(\mathrm{Na}\) (d) \(\mathrm{Br}\) (e) Xe (f) \(\mathrm{Fe}\)

Give the symbol for each of the following elements: (a) barium (b) titanium (c) chromium (d) lead (e) arsenic (f) zinc

Give the symbol for each of the following elements: (a) silver (b) aluminum (c) plutonium (d) tin (e) technetium (f) krypton

In each of the following pairs, decide which is an element and which is a compound. (a) Na or NaCl (b) sugar or carbon (c) gold

In each of the following pairs, decide which is an element and which is a compound. (a) \(\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\) or \(\mathrm{Pt}\) (b) copper or copper(II) oxide (c) silicon or sand

An 18 g sample of water is decomposed into \(2 \mathrm{g}\) of hydrogen gas and \(16 \mathrm{g}\) of oxygen gas. What masses of hydrogen and oxygen gases would have been prepared from 27 g of water? What law of chemistry is used in solving this problem?

A sample of the compound magnesium oxide is synthesized as follows. 60. g of magnesium is burned and produces \(100 .\) g of magnesium oxide, indicating that the magnesium combined with 40\. g of oxygen in the air. If \(30 .\) g of magnesium had been used, what mass of oxygen would have combined with it? What law of chemistry is used in solving this problem?

In each case, decide if the underlined property is a physical or chemical property. (a) The color of elemental bromine is orange-red. (b) Iron turns to rust in the presence of air and water. (c) Hydrogen can explode when ignited in air (Figure 1.16 ). (d) The density of titanium metal is \(4.5 \mathrm{g} / \mathrm{cm}^{3} .\) (e) Tin metal melts at \(505 \mathrm{K}\) (f) Chlorophyll, a plant pigment, is green.

In each case, decide if the change is a chemical or physical change. (a) \(\mathrm{A}\) cup of household bleach changes the color of your favorite T-shirt from purple to pink. (b) Water vapor in your exhaled breath condenses in the air on a cold day. (c) Plants use carbon dioxide from the air to make sugar. (d) Butter melts when placed in the Sun.

Which part of the description of a compound or element refers to its physical properties and which to its chemical properties? (a) The colorless liquid ethanol burns in air. (b) The shiny metal aluminum reacts readily with orange-red bromine.

Which part of the description of a compound or element refers to its physical properties and which to its chemical properties? (a) Calcium carbonate is a white solid with a density of \(2.71 \mathrm{g} / \mathrm{cm}^{3} .\) It reacts readily with an acid to produce gaseous carbon dioxide. (b) Gray, powdered zinc metal reacts with purple iodine to give a white compound.

The flashlight in the photo does not use batteries. Instead, you move a lever, which turns a geared mechanism and finally results in light from the bulb. What type of energy is used to move the lever? What type or types of energy are produced? (IMAGE CAN'T COPY)

A solar panel is pictured in the photo. When light shines on the panel, it generates an electric current that can be used to recharge the batteries in an electric car. What types of energy are involved in this setup?

Determine which of the following represent potential energy and which represent kinetic energy. (a) thermal energy (b) gravitational energy (c) chemical energy (d) electrostatic energy

Determine whether kinetic energy is being converted to potential energy, or vice versa, in the following processes. (a) Water cascades downward in a waterfall. (b) A player kicks a football. (c) An electric current is generated by a chemical reaction in a battery. (d) Water boils when heated on a gas stove.

A hot metal block is plunged into water in a well-insulated container. The temperature of the metal block goes down, and the temperature of the water goes up until their temperatures are the same. A total of \(1500 \mathrm{J}\) of energy is lost by the metal object. By how much did the energy of the water increase? What law of science is illustrated by this problem?

A book is held at a height above the floor. It has a certain amount of potential energy. When the book is released, its potential energy is converted to kinetic energy as it falls to the floor. The book hits the floor and comes to rest. According to the law of conservation of energy the amount of energy in the universe is constant. Where has the energy gone?

A piece of turquoise is a blue-green solid; it has a density of \(2.65 \mathrm{g} / \mathrm{cm}^{3}\) and a mass of \(2.5 \mathrm{g}\) (a) Which of these observations are qualitative and which are quantitative? (b) Which of the observations are extensive and which are intensive? (c) What is the volume of the piece of turquoise?

Iron pyrite (fool's gold, page 11 ) has a shiny golden metallic appearance. Crystals are often in the form of perfect cubes. A cube 0.40 cm on each side has a mass of 0.064 g. (a) Which of these observations are qualitative and which are quantitative? (b) Which of the observations are extensive and which are intensive? (c) What is the density of the sample of iron pyrite?

Which observations below describe chemical properties? (a) Sugar is soluble in water. (b) Water boils at \(100^{\circ} \mathrm{C}\) (c) Ultraviolet light converts \(\mathrm{O}_{3}\) (ozone) to \(\mathrm{O}_{2}\) (oxygen). (d) Ice is less dense than water.

28\. Which observations below describe chemical properties? (a) Sodium metal reacts violently with water. (b) The combustion of octane (a compound in gasoline) gives \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\) (c) Chlorine is a green gas.

You have a solution of NaCl dissolved in water. Describe a method by which these two compounds could be separated.

Small chips of iron are mixed with sand (see photo). Is this a homogeneous or heterogeneous mixture? Suggest a way to separate the iron from the sand. (IMAGE CAN'T COPY)

Identify the following as either physical changes or chemical changes. (a) Dry ice (solid \(\mathrm{CO}_{2}\) ) sublimes (converts directly from solid to gaseous \(\mathrm{CO}_{2}\) ). (b) Mercury's density decreases as the temperature increases. (c) Energy is given off as heat when natural gas (mostly methane, \(\mathrm{CH}_{4}\) ) burns. (d) NaCl dissolves in water.

Identify the following as either physical changes or chemical changes. (a) The desalination of sea water (separation of pure water from dissolved salts). (b) The formation of \(\mathrm{SO}_{2}\) (an air pollutant) when coal containing sulfur is burned. (c) Silver tarnishes. (d) Iron is heated to red heat.

Carbon tetrachloride, \(\mathrm{CCl}_{4}\), a common liquid compound, has a density of \(1.58 \mathrm{g} / \mathrm{cm}^{3} .\) If you place a piece of a plastic soda bottle \(\left(d=1.37 \mathrm{g} / \mathrm{cm}^{3}\right)\) and a piece of aluminum \(\left(d=2.70 \mathrm{g} / \mathrm{cm}^{3}\right)\) in liquid \(\mathrm{CCl}_{4},\) will the plastic and aluminum float or sink?

Categorize each of the following as an element, compound, or a mixture. (a) sterling silver (b) carbonated mineral water (c) tungsten (d) aspirin

Categorize each of the following as an element, a compound, or a mixture. (a) air (c) brass (b) fluorite (d) 18 -carat gold

Make a drawing, based on the kinetic-molecular theory and the ideas about atoms and molecules presented in this chapter, of the arrangement of particles in each of the cases listed here. For each case, draw 10 particles of each substance. It is acceptable for your diagram to be two dimensional. Represent each atom as a circle, and distinguish each different kind of atom by shading. (a) a homogeneous mixture of water vapor and helium gas (which consists of helium atoms) (b) a heterogeneous mixture consisting of liquid water and solid aluminum; show a region of the sample that includes both substances (c) a sample of brass (which is a homogeneous solid mixture of copper and zinc)

Hexane \(\left(\mathrm{C}_{6} \mathrm{H}_{14}, \text { density }=0.766 \mathrm{g} / \mathrm{cm}^{3}\right),\) perfluorohexane \(\left(\mathrm{C}_{6} \mathrm{F}_{14}, \text { density }=1.669 \mathrm{g} / \mathrm{cm}^{3}\right),\) and water are immiscible liquids; that is, they do not dissolve in one another. You place \(10 \mathrm{mL}\) of each in a graduated cylinder, along with pieces of high-density polyethylene (HDPE, density = 0.97 g/cm^{3 ), poly- } vinyl chloride (PVC, density = \(1.36 \mathrm{g} / \mathrm{cm}^{3}\) ), and Teflon (density \(=2.3 \mathrm{g} / \mathrm{cm}^{3}\) ). None of these common plastics dissolves in these liquids. Describe what you expect to see.

You have a sample of a white crystalline substance from your kitchen. You know that it is either salt or sugar. Although you could decide by taste, suggest another property that you could use to decide. (Hint: You may use the World Wide Web or a handbook of chemistry in the library to find some information.

You are given a sample of a silvery metal. What information could you use to prove the metal is silver?

Milk in a glass bottle was placed in the freezing compartment of a refrigerator overnight. By morning, a column of frozen milk emerged from the bottle. Explain this observation. (IMAGE CAN'T COPY)

Describe an experimental method that can be used to determine the density of an irregularly shaped piece of metal.

Diabetes can alter the density of urine, so urine density can be used as a diagnostic tool. Diabetics can excrete too much sugar or excrete too much water. What do you predict will happen to the density of urine under each of these conditions? (Hint: Water containing dissolved sugar is more dense than pure water.

Suggest a way to determine if the colorless liquid in a beaker is water. How could you discover if there is salt dissolved in the water?

Three liquids of different densities are mixed. Because they are not miscible (do not form a homogeneous solution with one another), they form discrete layers, one on top of the other. Sketch the result of mixing carbon tetrachloride \(\left(\mathrm{CCl}_{4}, d=\right.\) \(\left.1.58 \mathrm{g} / \mathrm{cm}^{3}\right),\) mercury \(\left(d=13.546 \mathrm{g} / \mathrm{cm}^{3}\right),\) and water \(\left(d=1.00 \mathrm{g} / \mathrm{cm}^{3}\right)\)

A copper-colored metal is found to conduct an electric current. Can you say with certainty that it is copper? Why or why not? Suggest additional information that could provide unequivocal confirmation that it is copper.

The photo below shows elemental iodine dissolving in ethanol to give a solution. Is this a physical or chemical change? (IMAGE CAN'T COPY)

You want to determine the density of a compound but have only a tiny crystal, and it would be difficult to measure mass and volume accurately. There is another way to determine density, however, called the flotation method. If you placed the crystal in a liquid whose density is precisely that of the substance, it would be suspended in the liquid, neither sinking to the bottom of the beaker nor floating to the surface. However, for such an experiment you would need to have a liquid with the precise density of the crystal. You can accomplish this by mixing two liquids of different densities to create a liquid having the desired density. (a) Consider the following: you mix \(10.0 \mathrm{mL}\) of \(\mathrm{CHCl}_{3}(d=1.492 \mathrm{g} / \mathrm{mL})\) and \(5.0 \mathrm{mL}\) of \(\mathrm{CHBr}_{3}\) \((d=2.890 \mathrm{g} / \mathrm{mL}),\) giving \(15.0 \mathrm{mL}\) of solution. What is the density of this mixture? (b) Suppose now that you wanted to determine the density of a small yellow crystal to confirm that it is sulfur. From the literature, you know that sulfur has a density of \(2.07 \mathrm{g} / \mathrm{cm}^{3} .\) How would you prepare \(20.0 \mathrm{mL}\) of the liquid mixture having that density from pure samples of \(\mathrm{CHCl}_{3}\) and \(\mathrm{CHBr}_{3} ?\left(\text {Note: } 1 \mathrm{mL}=1 \mathrm{cm}^{3} .\right)\)

A few years ago a young chemist in Vienna, Austria, wanted to see just how permanent the gold was in his wedding band. The ring was 18 -carat gold. (18-carat gold is \(75 \%\) gold with the remainder copper and silver.) One week after his wedding day he took off the ring, cleaned it carefully, and weighed it. It had a mass of 5.58387 g. He weighed it weekly from then on, and after 1 year it had lost \(6.15 \mathrm{mg}\) just from normal wear and tear. He found that the activities that took the greatest toll on the gold were vacationing on a sandy beach and gardening. (a) What are the symbols of the elements that make up 18-carat gold? (b) The density of gold is \(19.3 \mathrm{g} / \mathrm{cm}^{3} .\) Use one of the periodic tables on the Internet (such as www.ptable.com) to find out if gold is the most dense of all of the known elements. If it is not gold, then what element is the most dense [considering only the elements from hydrogen (H) through uranium (U)]? (c) If a wedding band is 18 -carat gold and has a mass of \(5.58 \mathrm{g}\), what mass of gold is contained within the ring? (d) Assume there are 56 million married couples in the United States, and each person has an 18-carat gold ring. What mass of gold is lost by all the wedding rings in the United States in 1 year (in units of grams) if each ring loses \(6.15 \mathrm{mg}\) of mass per year? Assuming gold is \(\$ 1620\) per troy ounce (where 1 troy ounce \(=\) 31.1 \(\mathrm{g}\) ), what is the lost gold worth?