Question

Define the following terms.
(a) Latent heat of fusion.
(b) Melting point.
(c) Fusion.

Answer 1

a) Latent heat of fusion.

The amount of heat energy absorbed / released when a solid changing to liquid at atmospheric pressure at its melting point is known as the latent heat of fusion. 

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b)Melting point.

Melting point is the temperature of a solid , at which it changes its state from solid to liquid at atmospheric pressure. 
The melting point of a substance ,  depends upon the atmospheric pressure.

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(c) Fusion.

When a solid is heated to change its solid  state into liquid form , this process is known as fusion.

Answer 2

a) latent heat of fusion : -
Latent heat of fusion is the heat required to change 1 kg of a solid substance into liquid state at the melting point of the substance. For example, amount of heat required to melt ice at 0° C into water at 0° C, will be known as the Latent Heat of Fusion of ice.

b) melting point :-
Melting point is defined as the temperature at which a substance changes from the solid state into the liquid state at atmospheric pressure. For example, the melting point of ice is 273 K (or zero degree Celsius).

c) Fusion :-
It is the process in which a solid changes its state into liquid. This process is endothermic as, it requires heat.
For example, ice changes in to liquid water, with increase in temperature of ice, by absorbing heat from the surrounding.

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