Chapter 9

What is the difference between a hot object and a cold one?

From a molecular standpoint, explain how thermal energy is transferred from a hot object to a cold one.

What is a perpetual motion machine? Why can such a device not exist?

Define each of the following terms: a. heat b. energy c. work d. system e. surroundings f. exothermic reaction g. endothermic reaction h. enthalpy of reaction i. kinetic energy j. potential energy

Explain the difference between energy and power.

What happens to the temperature of the surroundings during an exothermic reaction? Endothermic reaction?

Which temperature scale(s) a. does not contain negative temperatures? b. sets the boiling point of water at \(212^{\circ}\) ? c. has the same size of degree as the Kelvin scale? d. splits the difference between the boiling and freezing of water into 100 equally spaced degrees?

What is heat capacity? How is it related to changes in temperature?

Why are fossil fuels so named? Where do they come from?

What are the environmental problems associated with fossil-fuel use?

What does a catalytic converter do?

What is the major cause of acid rain?

Explain how acid rain is formed and its effects on the environment and on building materials.

Explain the natural greenhouse effect.

A person obtains approximately \(2.5 \times 10^{3}\) Calories a day from his or her food. How much energy is that in a. calories? b. joules? c. kilowatt-hours?

Perform each of the following conversions: a. \(102^{\circ} \mathrm{F}\) to \({ }^{\circ} \mathrm{C}\) b. \(0 \mathrm{~K}\) to \({ }^{\circ} \mathrm{F}\) c. \(0^{\circ} \mathrm{C}\) to \(^{\circ} \mathrm{F}\) d. \(273 \mathrm{~K}\) to \({ }^{\circ} \mathrm{C}\)

The coldest temperature ever measured in the United States is \(-80^{\circ} \mathrm{F}\) on January 23,1971 , in Prospect Creek, Alaska. Convert that temperature to Celsius and Kelvin.

The warmest temperature ever measured in the United States is \(134^{\circ} \mathrm{F}\) on July 10,1913 , in Death Valley,

A chocolate chip cookie contains about \(200 \mathrm{kcal}\). How many kilowatt- hours of energy does it contain? How long could you light a 100-W light bulb with the energy from the cookie?

An average person consumes about \(2.0 \times 10^{3} \mathrm{kcal}\) of food energy per day. How many kilowatt-hours of energy are consumed? How long could you light a 40-W light bulb with that energy?

Assume that electricity costs 15 cents per kilowatthour. Calculate the monthly cost of operating each of the following: a. a \(100-\mathrm{W}\) light bulb, \(5 \mathrm{~h} /\) day b. a \(600-\mathrm{W}\) refrigerator, \(24 \mathrm{~h} /\) day c. a \(12,000-\mathrm{W}\) electric range, \(1 \mathrm{~h} /\) day d. a \(1000-\mathrm{W}\) toaster, \(10 \mathrm{~min} /\) day

Assume that electricity costs 15 cents per kilowatthour. Calculate the yearly cost of operating each of the following: a. a home computer that consumes \(2.5 \mathrm{kWh}\) per week b. a pool pump that consumes \(300 \mathrm{kWh}\) per week c. a hot tub that consumes \(46 \mathrm{kWh}\) per week d. a clothes dryer that consumes \(20 \mathrm{kWh}\) per week

The useful energy that comes out of an energy transfer process is related to the efficiency of the process by the following equation: $$ \begin{aligned} &\text { total } \\ &\text { consumed } \end{aligned} \times \text { efficiency }=\begin{aligned} &\text { useful } \\ &\text { energy } \end{aligned} $$ where the efficiency is in decimal (not percent) form. a. If a process is \(30 \%\) efficient, how much useful energy can be derived if \(455 \mathrm{~kJ}\) are consumed? b. A person eats approximately \(2200 \mathrm{kcal} /\) day. How much of that energy is available to do physical work? c. If a car needs \(5.0 \times 10^{3} \mathrm{~kJ}\) to go a particular distance, how much energy will be consumed if the car is \(20 \%\) efficient? d. If an electrical power plant produces \(1.0 \times 10^{9} \mathrm{~J}\) of electrical energy, how much energy will be consumed by the plant if it is \(34 \%\) efficient?

Calculate the amount of carbon dioxide (in \(\mathrm{kg}\) ) emitted into the atmosphere by the complete combustion of a 15.0-gallon tank of gasoline. Do this by following these steps: a. Assume that gasoline is composed of octane \(\left(\mathrm{C}_{8} \mathrm{H}_{18}\right)\). Write a balanced equation for the combustion of octane. b. Determine the number of moles of octane contained in a 15.0-gallon tank of gasoline (1 gallon = \(3.78\) L). Octane has a density of \(0.79 \mathrm{~g} / \mathrm{mL}\). c. Use the balanced equation to convert from moles of octane to moles of carbon dioxide, then convert to grams of carbon dioxide, and finally to \(\mathrm{kg}\) of carbon dioxide.

The amount of \(\mathrm{CO}_{2}\) in the atmosphere is \(0.04 \%(0.04 \%\) \(=0.0004 \mathrm{~L} \mathrm{CO}_{2} / \mathrm{L}\) atmosphere). The world uses the equivalent of approximately \(4.0 \times 10^{12} \mathrm{~kg}\) of petroleum per year to meet its energy needs. Determine how long it would take to double the amount of \(\mathrm{CO}_{2}\) in the atmosphere due to the combustion of petroleum. Follow each of the steps outlined to accomplish this: a. We need to know how much \(\mathrm{CO}_{2}\) is produced by the combustion of \(4.0 \times 10^{12} \mathrm{~kg}\) of petroleum. Assume that this petroleum is in the form of octane and is combusted according to the following balanced reaction: $$ 2 \mathrm{C}_{8} \mathrm{H}_{18}(\mathrm{~L})+25 \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow 16 \mathrm{CO}_{2}(\mathrm{~g})+18 \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) $$ By assuming that \(\mathrm{O}_{2}\) is in excess, determine how many moles of \(\mathrm{CO}_{2}\) are produced by the combustion of \(4.0 \times 10^{12} \mathrm{~kg}\) of \(\mathrm{C}_{8} \mathrm{H}_{18}\). This will be the amount of \(\mathrm{CO}_{2}\) produced each year. b. By knowing that \(1 \mathrm{~mol}\) of gas occupies \(22.4 \mathrm{~L}\), determine the volume occupied by the number of moles of \(\mathrm{CO}_{2}\) gas that you just calculated. This will be the volume of \(\mathrm{CO}_{2}\) produced per year. c. The volume of \(\mathrm{CO}_{2}\) presently in our atmosphere is approximately \(1.5 \times 10^{18} \mathrm{~L}\). By assuming that all \(\mathrm{CO}_{2}\) produced by the combustion of petroleum stays in our atmosphere, how many years will it take to double the amount of \(\mathrm{CO}_{2}\) currently present in the atmosphere from just petroleum combustion?

The second law of thermodynamics has been called "the arrow of time." Explain why this is so.