Question

A piece of ice at $-{10}^{\circ }\text{C}$ is heated at a constant rate. The variation in its temperature with time, is shown in the graph below.

What is represented by the part $\text{AB}$ ?

• A. The melting of ice
• B. The heating of ice
• C. The boiling of water
• D. Decline in the temperature of water

Answer 1

The correct option is A The melting of ice

The ice, initially, is in the solid state below $0^{\circ }\text{C}$. On heating, its temperature rises above $0^{\circ }\text{C}$. It then takes some heat energy at $0^{\circ }\text{C}$ to melt completely into water at $0^{\circ }\text{C}$. This heat required is called the latent heat of fusion of ice. This phase is indicated in the graph as $\text{AB}$. During melting, the temperature remains constant, and hence, the slope of $\text{AB}$ is zero. Hence, $\text{AB}$ indicates the melting of ice into water, at a constant temperature of $0^{\circ }\text{C}$.

$\text{BC}$ indicates the rise of temperature of the water upto ${100}^{\circ }\text{C}$, whereas $\text{CD}$ indicates the phase change of water to steam, at a constant temperature of ${100}^{\circ }\text{C}$.