# Formula Temperature Change of a Substance Thermal energy    Temperature difference    Mass    Specific heat capacity

## Thermal energy

Unit
Thermal energy (also called heat) is the energy added to or released from a substance when it is brought from the initial temperature $$T_1$$ to the final temperature $$T_2$$.

## Temperature difference

Unit
It is the difference between the initial temperature and the final temperature, that is temperature by which the substance has become hotter or colder. In the case of the temperature difference, it does not matter whether the difference is formed by Kelvin temperatures or degree Celsius temperatures.

## Mass

Unit
Property of the substance under consideration that undergoes a temperature change. For example, $$1 \, \text{kg}$$ water is heated.

## Specific heat capacity

Unit
Specific heat capacity indicates how good a substance is at storing thermal energy. For example, to heat 1 kilogram of water by 1 Kelvin, a thermal energy of 4200 $$\text{J}$$ must be supplied to the water.

For example, water has a heat capacity $$c = 4200 \, \frac{\text{J}}{\text{kg} \, \text{K}}$$. The amount of water with mass $$m = 2\, \text{kg}$$ is heated from $$T_1 = 20^{\circ} \, \text{C}$$ to $$T_2 = 30^{\circ} \, \text{C}$$. So the temperature difference is $$\Delta T = 10^{\circ} \, \text{C}$$. That is $$10\, \text{K}$$. Thus, the thermal energy added to the water by heating is:\begin{align} \Delta Q &~=~ 4200 \, \frac{\text{J}}{\text{kg} \, \text{K}} ~\cdot~ 2\, \text{kg} ~\cdot~ 10 \, \text{K} \\\\ &~=~ 84 000 \, \text{J} \end{align}

That is $$84 \, \text{kJ}$$.