Question

When ice is converted into water at 0${}^{\circ }C$, it absorbs all the heat energy without an increase in its temperature. What is this heat energy known as?
A. Fermentation
B. Latent heat
C. Hidden heat
D. Normal heat

Answer 1

Hint: When ice is converting into water, it is undergoing the process of phase transformation. When a material is changing its phase, the process occurs at a particular constant temperature and some amount of heat energy is to be given for the process.

Complete answer:
Consider some volume of water at room temperature. We know that if we increase the temperature of the surroundings or heat the water, then the water will absorb some amount of energy (heat) and its temperature will increase.
The water will absorb heat until its temperature becomes equal to the temperature of the surrounding. If we increase the temperature further, at some temperature we see that the water starts to boil. And we also observe that when the water begins to boil, its temperature does not change
When the water boils, actually it is being converted into gas. Meaning it is changing its phase. The process of phase transformation takes place at a constant temperature. However, a certain amount of heat energy is required for phase transformation.
This heat required is called latent heat.
Similarly, when ice converts into water, there is phase transformation. And this process takes place at a constant temperature i.e. at 0${}^{\circ }C$. And the heat that has to be given for the phase transformation is called latent heat.

So, the correct answer is “Option B.

Note:
Note that phase transformation of a given material takes place at a particular temperature at a given pressure. We cannot change the phase of the material at any temperature.
Take the example of water. Water under the atmospheric pressure, can be converted into gas (i.e. water vapours) only at 100${}^{\circ }C$, called a boiling point of water.
And ice at the same pressure, can be converted into water only at 0${}^{\circ }C$called as melting point of ice.
This means that at different pressures, a material has different melting and boiling points.