Heat and Specific Heat Calculator (Q = m c ΔT)

Heat and temperature

Heat is energy transferred because of a temperature difference, measured in joules. When heat is added to an object that does not change phase, its temperature rises. The heat needed depends on the mass, the material and the temperature change:

Q = m × c × ΔT

Here m is the mass, c the specific heat and ΔT the final temperature minus the initial temperature.

What is specific heat?

Specific heat is the heat needed to raise the temperature of 1 kilogram of a material by 1 kelvin (1 °C). Its unit is J/(kg·K). Water has a very high specific heat (about 4186) and metals low ones (aluminium 900, iron 450, copper 385). That is why water is slow to heat and slow to cool, while a metal pan heats quickly.

Mass times specific heat is the heat capacity: the heat needed to raise the temperature of the object by 1 K.

Example

Heating 2 kg of water from 20 °C to 80 °C takes Q = 2 × 4186 × 60 = 502 320 J, or 502 kJ. That is about 0.14 kWh. The same heat given to 2 kg of copper would raise its temperature by 502 320 / (2 × 385) = 652 °C.

Sign

If the object warms, ΔT and Q are positive: it has gained heat. If it cools, both are negative: it has given heat off.

Limits

The formula holds only when there is no phase change. While ice melts at 0 °C and water boils at 100 °C the temperature stays constant and the heat goes into the change of phase. For water and ice the calculator refuses to give a result when these limits are crossed and tells you why. The specific heats in the list are approximate, so enter your own value for exact work.