Question

Explain the following Temperature versus Time graph.

Answer 1

In the given graph, line $AB$ represents conversion of ice into water at constant temperature. When ice is heated, it melts at $0^{0}C$ and converts into water maintaining constant temperature of $0^{0}C$. This constant temperature, at which the ice converts into water is called melting point of ice.
Also during this transition, the ice absorbs heat energy. This heat energy is utilised for weakening the bonds between the atoms or molecules in the ice to transform itself into liquid. This heat energy absorbed by ice, at constant temperature, to convert it into liquid is called the latent heat of fusion.
Once all the ice is transformed into water, the temperature of water rising. It
increases upto ${100}^{0}C$. Line $BC$ in the graph represents rise in
temperature of water from $0^{0}C$ to ${100}^{0}C$.
Thereafter, even though heat energy is supplied to water, its temperature does not rise. The heat energy is absorbed by water at this temperature and is used to break the bonds between molecules of the liquid and convert the
liquid into gaseous state. Thus, during transformation from liquid phase
to gas phase, heat energy is absorbed by the liquid, but its
temperature does not change.
The constant temperature at which liquid transforms into gaseous state is called boiling point of the liquid. The heat energy absorbed at constant temperature during transformation of liquid into gas is called the latent heat of vaporization.