Latent heat of fusion is the amount of heat energy required to change a substance from solid to liquid state without any change in temperature is called “heat of fusion’’.
The latent heat of fusion of water is 334 J/g or 80 cal/g. This means that to melt 1 gram of ice at 0°C, 334 J of heat energy must be added without any increase in temperature. Similarly, to freeze 1 gram of water at 0°C, 334 J of heat energy must be removed. The concept of latent heat of fusion is important in understanding phase changes and heat transfer in various physical and chemical processes.
The latent heat of vaporisation is the amount of energy required to change a substance from a liquid state to a gaseous state without a change in temperature is called “Heat of Vaporization”.
When water is heated on a stove, it reaches a temperature of 100°C. At this point, the energy being added to the water is used to break the intermolecular bonds between the water molecules. This results in the water molecules changing state from liquid to gas, which is known as vaporization.
During this phase change, the energy being added to the water does not raise the temperature of the water any further. Instead, it is used to overcome the intermolecular forces holding the water molecules together and allow them to separate and become water vapour. This energy is known as the latent heat of vaporisation, and it is a measure of the energy required to change a unit mass of a substance from liquid to gas at a constant temperature.
In the case of water, the latent heat of vaporization is about 2,260 kJ/kg. This means that for every kilogram of water that is boiled, 2,260 kJ of energy is required to convert it from a liquid to a gas.
This example of latent heat of vaporization can help students understand the concept of energy being used to change the state of a substance, and how this energy is not reflected in a change in temperature. This experiment has two parts: