Page 235 - Schaum's Outline of Theory and Problems of Applied Physics

220 HEAT [CHAP. 18

18.5. When a liquid evaporates
(a) it gives off heat (c) its temperature drops
(b) it absorbs heat (d) its temperature rises

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18.6. Which of the following substances requires the most heat per kilogram for a temperature rise of 1 C?
(a) water (c) steam
(b) ice (d) copper

18.7. The freezing point of water is 0 C. Its melting point is
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(a) slightly lower than 0 C
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(b) 0 C
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(c) slightly higher than 0 C
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(d)32 C
18.8. Food cooks faster in a pressure cooker than in an ordinary pot with a loose lid because the higher pressure
(a) forces heat into the food more rapidly
(b) lowers the boiling point of water
(c) raises the boiling point of water
(d) increases the specific heat capacity of water

18.9. In an hour a 1000-W electric heater produces
(a) 3.4 Btu (c) 3416 Btu
(b) 1054 Btu (d) 3600 Btu

18.10. When 20 kJ of heat is removed from 1.2 kg of ice originally at −15 C, its new temperature is
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(a) −18 C (c) −26 C
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(b) −23 C (d) −35 C
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18.11. A hot liquid at 80 C is added to 600 g of the same liquid originally at 10 C. When the mixture reaches 30 C, the
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total mass of liquid is
(a) 825 g
(b) 840 g
(c) 857 g
(d) Impossible to calculate without knowing the specific heat capacity of the liquid.
18.12. If 400 g of water at 10 C is poured into a 600-g pitcher [c = 0.80 kJ/(kg· C)] at 20 C, the final temperature of the
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water is
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(a) 11 C (c) 14 C
(b) 12 C (d) 17 C
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18.13. A 1.0-kg iron bar [c = 0.11 kcal/(kg· C)] at 100 C is placed in 3.0 kg of water at 15 C. The temperature of the
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water increases by
(a) 0.7 C (c) 5 C
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(b) 3 C (d) 18 C
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18.14. When 10 lb of water at 50 F is poured over 1.0 lb of ice at 0 F, the resulting mixture is at
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(a) 19 F (c) 32 F
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(b) 31 F (d) 34 F
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18.15. Which one or more of the following combinations will result in water at 50 C?
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