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Reviewed CSCA Physics question · Easy

In a sample of an ideal gas, the absolute temperature is doubled while the number of molecules and the volume are kept constant. What happens to the average translational kinetic energy of a single molecule?

  1. It becomes four times as large.
  2. It becomes twice as large.
  3. It becomes half as large.
  4. It remains unchanged.
Show the answer and explanation

Correct answer

B. It becomes twice as large.

Principle or equation

The average translational kinetic energy of a molecule in an ideal gas is directly proportional to the absolute temperature: KE_avg = (3/2) k_B T.

Why this answer is correct

Since KE_avg is proportional to T, doubling the absolute temperature doubles the average translational kinetic energy.

Example

If T increases from 300 K to 600 K, KE_avg doubles.

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