MCAT Physics Question 37: Answer and Explanation

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Question: 37

7. In an adiabatic compression process, the internal energy of the gas:

  • A. increases because the work done on the gas is negative.
  • B. increases because the work done on the gas is positive.
  • C. decreases because the work done on the gas is negative.
  • D. decreases because the work done on the gas is positive.

Correct Answer: B

Explanation:

To answer the question, make sure you understand all the terms. An adiabatic process means that there is no exchange of heat; in other words, Q = 0. When a gas is compressed, positive work is being done on the gas (rather than by the gas), so the value for work done by the gas will be negative (W < 0). Based on this, we can determine how the internal energy of the gas changes by using the first law of thermodynamics (ΔU = Q ? W). If Q = 0 and W is negative, then ΔU is positive.

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