(a) The melting point of naphthalene is 80° C and the room temperature is 25°. A sample of liquid naphthalene at 90° is cooled down to room temperature. Draw a temperature-time graph to represent this cooling. On the graph mark the region which corresponds to the freezing process.

(b) It takes a much longer time to boil off (change to steam) a certain quantity of water rather than bring it to its boiling point from room temperature, say 25°C. Explain the reason for this.

(a) Temperature-time graph representing the cooling of naphthalene from 90°C to room temperature of 20°C is shown below:

(b) The time taken to boil water involves two main steps: raising the temperature to the boiling point and then converting it to steam. Initially, energy is used to increase the temperature of water (say 25°C to 100°C), and this process takes time. Once the water reaches its boiling point, additional energy is required to undergo the phase change from liquid to vapour (steam), known as the latent heat of vaporization. This extra energy input during the phase transition contributes to the overall time it takes to boil water compared to just reaching the boiling point.