Why does the temperature of a substance remain constant during its melting point or boiling point

Answer: The temperature of a substance remains constant during melting and boiling points till the completion of melting and boiling because of the latent heat of fusion used by the substances. Latent heat of fusion helps to overcome the force of attraction between particles of solid to change into a liquid when they melt. Hence temperature remains constant.

In the same way during the formation of vapours, latent heat helps solid substance to convert into a gaseous state. Hence temperature of a substance remains constant at boiling point.

Answer:

The temperature of a substance remains constant during melting and boiling points till the completion of melting and boiling. It is because substance makes use of latent heat of fusion to overcome force of attraction between particles of solid to change into liquid during melting and latent heat of vaporization to overcome force of attraction between particles of liquid to change into vapours during boiling. Therefore, temperature remains constant.

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Text Solution

Solution : As long as a substance has not started either melting or boiling, the heat energy supplies increases the kinetic energy of the particles. Therefore, the temperature of the substance increases. Once it starts melting or boiling , the further heat energy is absorbed either as latent heat of fusion or as latent heat of vaporisation. This does not cause any increase in kinetic energy because all the particles of a substance have sufficient kinetic energy to change into liquid or vapour state. However, interparticle forces do not allow them to do so. The energy supplied simply overcomes these interparticle forces and they undergo change in state.

Text Solution

Solution : The temperature of a substance remains constant during melting and boiling points till the completion of melting and boiling. It is because substance makes use of latent heat of fusion to overcome force of attraction between particles of solid to change into liquid during melting and latent heat of vaporisation to overcome force of attraction between particles of liquid to change into vapours during boiling. <br> Therefore, temperature remains constant.

The temperature of a substance remains constant at its melting and boiling points until all the substance melts or boils because, the heat supplied is continuously used up in changing the state of the substance by overcoming the forces of attraction between the particles. This heat energy absorbed without showing any rise in temperature is given the name latent heat of fusion/latent heat of vaporisation.

The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.
The temperature at which a liquid boils and changes rapidly into a gas at the atmospheric pressure is called its boiling point. Boiling point if water is 100oC

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