What does the term "heat capacity" measure?

The term "heat capacity" specifically measures the amount of heat required to raise the temperature of a substance by a given amount, usually expressed in degrees Celsius or Kelvin. It reflects how much thermal energy a material can store for a given temperature change, which is crucial in understanding thermal dynamics and energy transfer in engineering applications.

This property is essential because different substances have varying capacities to absorb and retain heat; for instance, water has a high heat capacity, which is why it can absorb a lot of heat without a significant change in temperature. This characteristic is critical when designing systems involving heat exchangers, boilers, and other thermal systems, as it influences material choice and system efficiency.

The other options such as the heat lost during a phase change, the total energy of a substance at any temperature, and the energy retained after performing work do not accurately define heat capacity. Each of these concepts pertains to different aspects of thermodynamics and energy transfer, but they do not directly describe the thermal property indicated by heat capacity, which focuses specifically on the relationship between heat input and temperature increase.