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10. Explain how the latent heat of fusion and the latent heat of 4. Analyze the table of specific heats (Table 4.2) and determine
vaporization are “hidden.” which metal would make an energy-efficient and practical pan,
11. What is condensation? Explain, on a molecular level, how the providing more cooking for less energy.
condensation of water vapor on a bathroom mirror warms the 5. This chapter contains information about three types of passive solar
bathroom. home design. Develop criteria or standards of evaluation that would
12. Which provides more cooling for a Styrofoam cooler: 10 lb of ice help someone decide which design is right for her or his local
at 0°C or 10 lb of ice water at 0°C? Explain your reasoning. climate.
13. Explain why a glass filled with a cold beverage seems to “sweat.” 6. Could a heat pump move heat without the latent heat of
Would you expect more sweating inside a house during the vaporization? Explain.
summer or during the winter? Explain. 7. Explore the assumptions on which the “heat death of the
14. Explain why a burn from 100°C steam is more severe than a burn universe” idea is based. Propose and evaluate an alternative idea
from water at 100°C. for the future of the universe.
15. Briefly describe, using sketches as needed, how a heat pump is
able to move heat from a cooler region to a warmer region.
INVITATION TO INQUIRY
16. Which has the greatest entropy: ice, liquid water, or water vapor?
Explain your reasoning. Who Can Last Longest?
17. Suppose you use a heat engine to do the work to drive a heat How can we be more energy efficient? Much of our household energy
pump. Could the heat pump be used to provide the temperature
consumption goes into heating and cooling, and much energy is lost
difference to run the heat engine? Explain.
through walls and ceilings. This invitation is about the insulating prop-
erties of various materials and their arrangement.
FOR FURTHER ANALYSIS The challenge of this invitation is to create an insulated container
that can keep an ice cube from melting. Decide on a maximum size for
1. Considering the criteria for determining if something is a solid, the container, and then decide what materials to use. Consider how
liquid, or gas, what is table salt, which can be poured?
you will use the materials. For example, if you are using aluminum foil,
2. What are the significant similarities and differences between heat should it be shiny side in or shiny side out? If you are using newspapers,
and temperature?
should they be folded flat or crumpled loosely?
3. Gas and plasma are phases of matter, yet gas runs a car and One ice cube should be left outside the container to use as a con-
plasma is part of your blood. Compare and contrast these terms
trol. Find out how much longer your insulated ice cube will outlast
and offer an explanation for the use of similar names.
the control.

PARALLEL EXERCISES

The exercises in groups A and B cover the same concepts. Solutions to group A exercises are located in appendix E.

Note: Neglect all frictional forces in all exercises.
Group A Group B

1. The average human body temperature is 98.6°F. What is the 1. The Fahrenheit temperature reading is 98° on a hot summer day.
equivalent temperature on the Celsius scale? What is this reading on the Kelvin scale?
2. An electric current heats a 221 g copper wire from 20.0°C to 2. A 0.25 kg length of aluminum wire is warmed 10.0°C by an
38.0°C. How much heat was generated by the current? electric current. How much heat was generated by the current?
(c copper = 0.093 kcal/kgC°) (c aluminum = 0.22 kcal/kgC°)
3. A bicycle and rider have a combined mass of 100.0 kg. How 3. A 1,000.0 kg car with a speed of 90.0 km/h brakes to a stop. How
many calories of heat are generated in the brakes when the many calories of heat are generated by the brakes as a result?
bicycle comes to a stop from a speed of 36.0 km/h?
4. A 15.53 kg loose bag of soil falls 5.50 m at a construction site. If 4. A 1.0 kg metal head of a geology hammer strikes a solid rock
all the energy is retained by the soil in the bag, how much will its with a velocity of 5.0 m/s. Assuming all the energy is retained by
temperature increase? (c soil = 0.200 kcal/kgC°) the hammer head, how much will its temperature increase?
(c head = 0.11 kcal/kgC°)
5. A 75.0 kg person consumes a small order of french fries 5. A 60.0 kg person will need to climb a 10.0 m stairway how many
(250.0 Cal) and wishes to “work off” the energy by climbing a times to “work off” each excess Cal (kcal) consumed?
10.0 m stairway. How many vertical climbs are needed to use all
the energy?
6. A 0.5 kg glass bowl (c glass = 0.2 kcal/kgC°) and a 0.5 kg iron pan 6. A 50.0 g silver spoon at 20.0°C is placed in a cup of coffee at
(c iron = 0.11 kcal/kgC°) have a temperature of 68°F when placed 90.0°C. How much heat does the spoon absorb from the coffee to
in a freezer. How much heat will the freezer have to remove from reach a temperature of 89.0°C?
each to cool them to 32°F?

112 CHAPTER 4 Heat and Temperature 4-28