Amount of heat energy required to heat a body is a function of its mass, required temperature change, its phase and material properties. The given equation for heat energy is:
`q = mcDeltaT`
where, q is the amount of heat energy gained or lost by a material, m is its mass, c is the specific heat capacity and `DeltaT` is the change in its temperature.
The specific heat capacity is defined as the amount of heat required to increase the temperature of a gram of a substance by 1 degree Celsius. The values of specific heat capacity for various solid and liquids is known. For example, water has a specific heat capacity of 4.184 J/gm/degree C.
An example problem could be: Calculate the amount of heat required to raise the temperature of a cup of water (capacity = 250 ml) from 20 degree Celsius to 90 degree Celsius for making tea.
Here, mass = 250 ml = 250 g (since density of water is about 1 g/ml).
Thus, heat required = 250 g x 4.184 J/g/degree C x (90 - 20)
= 73,220 J = 73.22 kJ.
Hope this helps.