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TABLE 4.2

The specific heat of selected substances
Substance Specific Heat (cal/gC° or kcal/kgC°)
Air 0.17
Aluminum 0.22
Concrete 0.16
Copper 0.093
Glass (average) 0.160
Gold 0.03
Transmission of
Ice 0.500 increased kinetic energy
Iron 0.11
Lead 0.0305
Mercury 0.033
Seawater 0.93
Silver 0.056
Soil (average) 0.200
Steam 0.480
Water 1.00

Note: To convert to specific heat in J/kgC°, multiply each value by 4,184. Also note
that 1 cal/gC° = 1 kcal/kgC°.

FIGURE 4.13 Thermometers placed in holes drilled in a metal
CONCEPTS Applied rod will show that heat is conducted from a region of higher tem-
perature to a region of lower temperature. The increased molecular
More Kitchen Physics activity is passed from molecule to molecule in the process of
conduction.
Consider the following information as it relates to the
metals of cooking pots and pans.
1. It is easier to change the temperature of metals with
low specific heats. region of lower temperature. In solids, this transfer takes place
2. It is harder to change the temperature of metals with as heat is conducted from a warmer place to a cooler one. Recall

high specific heats. that the molecules in a solid vibrate in a fixed equilibrium posi-
tion and that molecules in a higher-temperature region have
Look at the list of metals and specific heats in Table 4.2
and answer the following questions: more kinetic energy, on the average, than those in a lower-
temperature region. When a solid, such as a metal rod, is held
1. Considering specific heat alone, which metal could be

in a flame, the molecules in the warmed end vibrate violently.
used for making practical pots and pans that are the

Through molecular interaction, this increased energy of vibra-
most energy efficient to use?
2. Again considering specific heat alone, would certain tion is passed on to the adjacent, slower-moving molecules,

combinations of metals provide any advantages for which also begin to vibrate more violently. They, in turn, pass
rapid temperature changes? on more vibrational energy to the molecules next to them. Th e
increase in activity thus moves from molecule to molecule,
causing the region of increased activity to extend along the rod.

This is called conduction, the transfer of energy from molecule
HEAT FLOW to molecule (Figure 4.13).
Most insulating materials are good insulators because
In the “Heat as Energy Transfer” section, you learned the process

of heating is a transfer of energy involving (1) a temperature dif- they contain many small air spaces (Figure 4.14). The small air
ference or (2) energy-form conversions. Heat transfer that takes spaces are poor conductors because the molecules of air are

place because of a temperature difference takes place in three far apart, compared to a solid, making it more diffi cult to pass

different ways: by conduction, convection, or radiation. the increased vibrating motion from molecule to molecule.
Styrofoam, glass wool, and wool cloth are good insulators
because they have many small air spaces, not because of the
Conduction material they are made of. The best insulator is a vacuum,

Anytime there is a temperature difference, there is a natural since there are no molecules to pass on the vibrating motion

transfer of heat from the region of higher temperature to the (Table 4.3).
96 CHAPTER 4 Heat and Temperature 4-12