Question

1A: During a process, 28 J of heat are transferred into a system, while the system itself does 14 J of work. What is the change in the internal energy of the system?
   __________ J

1B: If the internal energy of an ideal gas increases by 170 J when 250 J of work are done to compress it, how much heat is released?
   __________ J

1C: It takes 270 cal to raise the temperature of a metallic ring from 20°C to 30°C. If the ring has a mass of 75 g, what is the specific heat of the metal?
   __________ cal/g·°C

1D: If it takes 3400 cal to raise the temperature of a 490 g statue by 44°C, what is the specific heat of the material used to make the statue?
__________ cal/g·°C

Answer 1

1A: Change in internal energy of the system= heat transferred into the system- work done by the system = 28J - 14 J = 14 J

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1B: Work done by the gas = -work done on it = -250J ;

Now, change in internal energy of the gas= heat given to gas - work done by gas

So, 170J = heat given to gas- (-250J) = heat given to gas+ 250J

So, heat given to gas= 170J- 250J = -80J

Heat given is negative, so heat is released by gas= 80J

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1C: Heat required to raise temperature= specific heat* mass* temperature change

So, 270= specific heat*75*(30-20)

So, specific heat= 0.36cal/g·°C

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1D: Similarly, 3400= specific heat* 490* 44

So, specific heat of the material used to make the statue= 0.1577cal/g·°C