Physics for Scientists and Engineers, 6e

1. Physics for Scientists and Engineers, 6e Chapter 20 – Heat and the First Law of Thermodynamics

2. Imagine you have 1 kg each of iron, glass, and water, and that all three samples are at 10°C. Rank the samples from lowest to highest temperature after 100 J of energy is added to each sample. • iron, glass, water • iron, water, glass • glass, iron, water • glass, water, iron • water, glass, iron • water, iron, glass

3. Because water has the highest specific heat (4 186 J/kg · °C), it has the smallest change in temperature. Glass is next (837 J/kg · °C), and iron is last (448 J/kg · °C).

4. Imagine you have 1 kg each of iron, glass, and water, and that all three samples are at 10°C. Rank them from least to greatest amount of energy transferred by heat if each sample increases in temperature by 20°C. • iron, glass, water • iron, water, glass • glass, iron, water • glass, water, iron • water, glass, iron • water, iron, glass

5. Iron, glass, water. For a given temperature increase, the energy transfer by heat is proportional to the specific heat.

6. Calculate the slopes for the A, C, and E portions of the figure below. Rank the slopes from least to greatest. • A, C, E • A, E, C • C, E, A • C, A, E • E, A, C • E, C, A

7. C, A, E. The slope is the ratio of the temperature change to the amount of energy input. Thus, the slope is proportional to the reciprocal of the specific heat. Water, which has the highest specific heat, has the smallest slope.

8. Characterize path A in the figure below: • isobaric • isovolumetric • isothermal • adiabatic

9. Characterize path B in the figure below. Note that Q = 0. • isobaric • isovolumetric • isothermal • adiabatic

10. Characterize path C in the figure below: • isobaric • isovolumetric • isothermal • adiabatic

11. Characterize path D in the figure below: • isobaric • isovolumetric • isothermal • adiabatic

12. An ice cube wrapped in a wool blanket will remain frozen for a _____ length of time than an identical ice cube exposed to air at room temperature. • shorter • same • longer

13. The blanket acts as a thermal insulator, slowing the transfer of energy by heat from the air into the cube.

14. You have two rods of the same length and diameter but they are formed from different materials. The rods will be used to connect two regions of different temperature such that energy will transfer through the rods by heat. They can be connected in series, as in part (a) of the figure below, or in parallel, as in part (b). In which case is the rate of energy transfer by heat larger? • when the rods are in series • when the rods are in parallel • The rate is the same in both cases.

15. In parallel, the rods present a larger area through which energy can transfer and a smaller length.