Latent Heat
Latent Heat
Latent Heat Of Vaporisation:
The latent heat of vaporisation of a substance is defined as the quantity of heat gained by 1 kg of the substance in changing from liquid to vapour state or from vapour to liquid state at constant temperature.
When you heat a liquid, its molecules start moving faster and gain kinetic energy. This shows as a rise in its temperature. At the boiling point, however, the heat supplied is used by the molecules to break away from the inter-molecular force and change into vapour molecules, rather than to move faster.This is why there is no change in the temperature. The heat required to help the molecules of liquid to overcome the inter-molecular forces and to escape as a vapour molecules is known as the latent heat of vaporisation.
Latent Heat Of Fusion:
The latent heat of fusion is defined as the quantity of heat gained by 1 kg of substance in changing from the solid to liquid at same temperature.
When a solid is heated, its molecules start vibrating faster and its temperature rises until it reaches the melting point. Then the temperature remains constant until the entire solid changes to liquid. The heat supplied during the process is used by the molecules to overcome the inter-molecular force, and not to raise the temperature.This heat is called the latent heat of fusion. It is gained by the solid molecules to change to liquid molecules at constant temperature.
In the reverse process, liquid molecules lose the latent heat of fusion to change to solid molecules at the freezing point. During this process too the temperature remains constant.
Which of the following are correct ? (a) The latent heat of vaporisation of a substance is defined as the quantity of heat gained by 1 kg of the substance in changing from liquid to vapour state . (b) The latent heat of fusion is defined as the quantity of heat gained by 1 kg of substance in changing from the solid to liquid . (c) At the boiling point the heat supplied is used by the molecules to break away from the inter-molecular force and change into vapour molecules. | |||
| Right Option : D | |||
| View Explanation | |||
The heat required to help the molecules of liquid to overcome the intermolecular forces and to escape as a vapour molecules is known as the _______________________ . | |||
| Right Option : C | |||
| View Explanation | |||
Which of the following are correct ? (a) The latent heat of fusion is defined as the quantity of heat gained by 1 kg of substance in changing from the liquid to solid at same temperature. (b) The latent heat supplied during the process is used by the molecules to overcome the intermolecular force, and not to raise the temperature. | |||
| Right Option : B | |||
| View Explanation | |||
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