Kaplan Nursing Entrance Practice Exam

What does temperature measure in a substance?

1. Volume of molecules

2. Mass of molecules

3. Average kinetic energy of molecules

4. Number of molecules present

The correct answer is: Average kinetic energy of molecules

Temperature measures the average kinetic energy of molecules in a substance. This concept stems from the kinetic molecular theory, which posits that the molecules of a substance are in constant motion. As the temperature of a substance increases, the average speed of these molecules increases as well, reflecting a higher average kinetic energy. This correlation is why temperature is an indicator of how energetic and active the molecules are within that substance. The other options do not accurately reflect what temperature signifies. Volume refers to the space a substance occupies, which is not directly related to the energy of the molecules. Mass pertains to the amount of matter in a substance and is not indicative of the motion or energy levels of the molecules. The number of molecules present can influence the substance's properties, but temperature itself does not measure this quantity. Understanding that temperature relates specifically to the average kinetic energy helps clarify its physical significance in the behavior of substances.