Question

How much energy is released or absorbed when 1gm of water at 0°C freezes to ice at 0°C?

Answer 1

Hint: To find out the amount of energy change in energy, the amount of energy released or absorbed by a certain mass of water is the amount of energy required for it to reach its freezing point temperature and the energy required for its change of state to ice from water.

Complete step-by-step solution -

Given data,
Mass of water = 1gm
Temperature = 0°C
Converted from water to ice.
We know the freezing point of water is 0°C or 32 F. The given water is already at its freezing point temperature. So here the energy change occurs only due to the change of state from water to ice.
The amount of energy required to convert a unit mass of water into ice, i.e. from liquid to solid without a change in its temperature is called the latent heat of fusion of water.
It is the energy change per unit mass of the substance for a phase change to occur at a certain temperature.
1 gm of water ------------------ 1 gm of ice + Latent heat of fusion.
The latent heat of fusion of water at 0°C is 334 Joules per gram of water.
Hence the energy released when 1gm of water at 0°C freezes to ice at 0°C is 334 J.

Note – In order to answer this type of questions the key is to know the concept of latent heat of fusion, when it occurs and the latent heat of fusion for some common phase changes in day to day life. Like melting, boiling and freezing. A similar concept of Latent heat of vaporization occurs when a liquid is converted into a gas. It is the energy required to convert a unit mass of liquid into gas.
It can be seen as the energy required to break the bonds of molecules of a liquid substance converting into gaseous state.
The Latent heat of vaporization of water is 2260 Kilojoules per Kg. It occurs at the boiling point of water i.e. at 100°C.