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Model Paper 5 — Science STD 9 — Question

Gujarat BoardEnglish MediumSTD 9ScienceModel Paper 52 Marks
Question
Why the temperature of boiling water does not rise even when heat is continuously supplied to it?
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Answer

The heat which is taken by the particles of water in liquid state is used to overcome the forces of attraction which are holding these particles together in the liquid state. When these particles change their state from liquid (at $100^{\circ} C$ ) to vapour state (at $100^{\circ} C$ ), they only absorb latent heat which is only $22.5 \times 10^5 J / kg$. This latent heat does not increase the kinetic energy of water particles in gaseous state and hence no rise in temperature takes place during the boiling of water.

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