Specific Heat Capacity

Temperature and heat are not the same thing:

• temperature is a measure of how hot something is
• heat is a measure of the thermal energy contained in an object.

Temperature is measured in °C, and heat is measured in J. When heat energy is transferred to an object, its temperature increase depends upon the:

• the mass of the object
• the substance the object is made from
• the amount energy transferred to the object.

For a particular object, the more heat energy transferred to it, the greater its temperature increase.

The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1 kg of the substance by 1°C. Different substances have different specific heat capacities.

Here is the equation relating energy to specific heat capacity:

E = m × c × θ

• E is the energy transferred in joules, J
• m is the mass of the substances in kg
• c is the specific heat capacity in J / kg/ °C
• θ (‘theta’) is the temperature change in degrees Celsius, °C

So the word equation is:

Change in thermal energy (J) = specific heat capacity (J/kg/°C) × mass (kg) × temperature change (°C)

For example, how much energy must be transferred to raise the temperature of 2 kg of water from 20°C to 30°C?

E = m × c × θ (θ = 30 – 20 = 10°C)

E = 2 × 4181 × 10 = 83,620 J or 83.62 kJ