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

• The boiling point of water is 100°C. The temperature of boiling water does not rise instead of continuous supply of heat, as the extra heat is supplied to the water is used to turn water into steam.
• Hence, steam has a lot of latent heat which can cause severe burns. That’s why Alka felt intense heat from the puff of steam gushing out of the spout of the kettle.
• The temperature of both boiling water and steam is 100°C, but steam gives out more heat (due to latent heat of vaporization) in comparison to boiling water.
• When water changes into steam, it absorbs latent heat of vaporization, but when steam condenses to form water, an equal amount of latent heat is given out without changing the temperature.