Energy, Heat and Work: Quiz
Seven questions on energy and its units, heat versus temperature, gas expansion work and the first law, with explanations.
Energy, Heat and Work: Quiz
7 questions
Temperature reflects the average particle energy; heat is energy in transit, always from hotter to colder. A large warm bath holds more thermal energy than a small cup of boiling water.
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Answer: Heat is energy transferred because of a temperature difference
Temperature reflects the average particle energy; heat is energy in transit, always from hotter to colder. A large warm bath holds more thermal energy than a small cup of boiling water.
E = ½mv² = ½ × 1000 kg × (20.0 m/s)² = 2.00 × 10⁵ J = 200. kJ. 400. kJ forgets the ½; 20.0 kJ forgets to square the speed.
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Answer: 200. kJ
E = ½mv² = ½ × 1000 kg × (20.0 m/s)² = 2.00 × 10⁵ J = 200. kJ. 400. kJ forgets the ½; 20.0 kJ forgets to square the speed.
250 kcal × 4.184 kJ/kcal = 1046 kJ = 1.05 × 10³ kJ. 59.8 kJ comes from dividing instead of multiplying.
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Answer: 1.05 × 10³ kJ
250 kcal × 4.184 kJ/kcal = 1046 kJ = 1.05 × 10³ kJ. 59.8 kJ comes from dividing instead of multiplying.
A rigid container cannot change volume, so no expansion work is done (ΔV = 0, w = 0). All the heat added raises the internal energy: ΔU = q.
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Answer: w = 0, so ΔU = q
A rigid container cannot change volume, so no expansion work is done (ΔV = 0, w = 0). All the heat added raises the internal energy: ΔU = q.
w = −PΔV = −3.00 atm × 2.00 L = −6.00 L·atm × 101.325 J/(L·atm) = −608 J. It is negative because the expanding gas does work on the surroundings.
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Answer: −608 J
w = −PΔV = −3.00 atm × 2.00 L = −6.00 L·atm × 101.325 J/(L·atm) = −608 J. It is negative because the expanding gas does work on the surroundings.
q = −300. J (heat out), w = +150. J (work on the system). ΔU = q + w = −300. J + 150. J = −150. J.
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Answer: −150. J
q = −300. J (heat out), w = +150. J (work on the system). ΔU = q + w = −300. J + 150. J = −150. J.
A closed system (e.g. a sealed flask) lets energy cross its boundary as heat or work, but not matter. An open system exchanges both; an isolated system exchanges neither.
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Answer: Closed
A closed system (e.g. a sealed flask) lets energy cross its boundary as heat or work, but not matter. An open system exchanges both; an isolated system exchanges neither.