What is temperature?

• A. The measure of the average kinetic energy of the molecules.
• B. The amount of heat required to raise the temperature by one degree.
• C. A form of energy stored in matter.
• D. A property that describes the object's heat content.

Answer: (A)

Temperature is a measure of the average kinetic energy of the molecules in a substance. When molecules jiggle and move, their speeds reflect how hot or cold something is; higher temperature means more rapid average motion. This concept explains why heat flows from warmer objects to cooler ones until they share the same temperature.

The other ideas describe related but different quantities: the heat required to raise temperature by one degree is heat capacity (or specific heat), which is about how much energy you need to add, not about how hot something is. Energy stored in matter refers to thermal energy or internal energy, not temperature itself. Describing a substance’s heat content again points to thermal energy, not the temperature. So the statement that best captures what temperature itself measures is the average kinetic energy of the molecules.