Question

In cold countries, water does not freeze all at once in ponds and lakes. This happens due to what?
A) High specific latent heat of fusion of ice
B) High specific latent heat of fusion of water
C) High specific latent heat of evaporation of ice
D) None

Answer 1

Hint: The specific latent heat of fusion is the physical property of the specific substance. The specific latent heat of fusion is the amount of energy needed to convert the state of the substance of \[1Kg\] without changing its temperature. The specific latent heat of fusion is used for the melting and freezing of water. And the specific latent heat of evaporation is used to convert the one mole of substance from its liquid state to the gaseous state.

Complete answer:
(i) In freezing, the bonds in the water fuses and the molecules are tightly packed.
(ii) As we know that the specific latent heat of evaporation is used for converting from liquid state to gaseous state, here in the question we have that the water freeze not vaporises. Hence option C is incorrect.
(iii) The specific heat of ice fusion of ice equals \[336J{g^{ - 1}}\]. It is used to change the ice into water. Here we have a question about freezing water which means converting water into ice. Hence option A is incorrect.
(iv)The specific latent heat of fusion of water is \[334J{g^{ - 1}}\]. It is the energy needed to convert the water into ice. As the \[334Joules\] is required to convert one gram of water, the high specific latent heat is used for the fusion of water.

Hence the correct option is (B).

Note:
(i)The latent heat is the amount of heat required to change the state of the substance. It is the amount of heat required to convert the solid to liquid, liquid to gas and the gas to solid etc. The latent heat is specific for substances.
(ii) According to the law of conservation of energy, the energy can neither be created nor be destroyed. It can only be converted from one form into another. Therefore, the heat energy released by the body cooled.