MCAT Physics Question 45: Answer and Explanation

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Question: 45

15. Which of the following processes is LEAST likely to be accompanied by a change in temperature?

  • A. The kinetic energy of a gas is increased through a chemical reaction.
  • B. Energy is transferred to a solid via electromagnetic waves.
  • C. A boiling liquid is heated on a hot plate.
  • D. A warm gas is mixed with a cold gas.

Correct Answer: C

Explanation:

If a substance is undergoing a phase change, any added heat will be used toward overcoming the heat of transformation of the phase change. During the phase change, the temperature will remain constant. Temperature is a measure of the kinetic energy of the molecules in a sample, so a change in kinetic energy, choice (A), is essentially the same thing as a change in temperature. The heat transfer by radiation described in choice (B) will definitely change the temperature of the solid as long as it is not in the process of melting. Choice (D) describes heat transfer by convection, in which the warm gas will transfer heat to the cold gas until they both reach an intermediate temperature.

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