Kaplan Nursing Entrance Practice Exam

What does temperature measure regarding a substance?

1. The pressure of gas within it

2. The total heat content of the substance

3. The average kinetic energy of its molecules

4. The density of the substance

The correct answer is: The average kinetic energy of its molecules

Temperature is a measure of the average kinetic energy of the molecules in a substance. When temperature increases, it indicates that the molecules are moving faster, reflecting higher kinetic energy. This concept is foundational in thermodynamics and explains how temperature is a fundamental property affecting the state of matter. The other options address distinct characteristics of a substance. For example, pressure relates to the force exerted by gas molecules and their collisions with the walls of a container, which is unrelated to the measurement of temperature. Total heat content, or enthalpy, involves both the kinetic energy of molecules and their potential energy, which is broader than just temperature. Density, a measure of mass per unit volume, does not directly correlate with temperature, as density can change with temperature but is not what temperature itself measures. Thus, the correct choice highlights the specific relationship between temperature and kinetic energy at the molecular level.