The temperature of an ideal gas is raised from to . By what factor does the r.m.s. speed of its molecules change?

Answer and explanation

Correct answer: D. It doubles

  1. Step 1: Mean kinetic energy is proportional to , and gives .
  2. Step 2: increases by a factor of , so the speed changes by .
Answer
It doubles.
Why not the others: It quadruples: is the factor for the mean kinetic energy, not the speed. It increases by a factor of : uses a temperature ratio of instead of . It stays the same: temperature affects molecular speed.

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