Question

Alka was making tea in a kettle. Suddenly she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle. Comment.

Answer 1

Latent Heat of Vaporization

• Latent heat of vaporization is the heat consumed or discharged when matter disintegrates, changing state from fluid to gas state at a consistent temperature.
• The latent heat of vaporization of water is about 2,260 kJ/kg.

Conversion of Water to Steam

• Continuous heat is supplied to the water for converting it into steam.
• The water starts boiling at $100°\mathrm{C}$.
• After that the temperature of the water does not increase but it absorbs latent heat of vaporization to convert it into steam.
• The temperature of the steam is the same as that of boiling water i.e. $100°\mathrm{C}$. But it has more heat energy as compared to boiling water.

Hence, the temperature of both boiling water and steam is 100°C, but steam gives out more heat in comparison to boiling water due to latent heat of vaporization.