Adding energy to a body can change its temperature. The amount required depends on both the body and its material.

The heat capacity $C$ of a body relates a small energy transfer to its temperature change:

$$Q\approx C\Delta T$$

when $C$ is approximately constant over the interval.

Specific heat capacity

A material property independent of total mass is the specific heat capacity $c$:

$$Q=mc\Delta T.$$

A material with larger $c$ requires more energy per unit mass to produce the same temperature change.

Heating does not always change temperature

During a phase change, energy can be transferred while temperature remains nearly constant. The simple relation $Q=mc\Delta T$ therefore describes sensible heating within one phase, not every thermal process.

Thermal energy storage

Heat capacity matters whenever a system's temperature changes in time: buildings, cooling systems, batteries, engines and transient heat-transfer problems all combine energy flow with the ability of materials to store internal energy.