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प्रश्न
Why does the temperature of a substance remain constant during its melting point or boiling point?
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उत्तर
When a substance melts, it absorbs heat for the conversion of the solid state into a liquid state. As we continue heating, the heat supplied is used up in converting the solid state into a liquid state by overcoming the forces of attraction between the particles and there is no change in temperature till the whole solid is converted into liquid. This heat absorbed by the solid which does not result in an increase in temperature is called the latent heat of fusion. When a liquid is heated, it starts converting into vapours.
Further heat given to the liquid is used in changing the state and there is no increase in the temperature till the liquid starts boiling. This heat is known as the latent heat of vaporisation. Hence, the temperature of a substance remains constant at its melting point or boiling point until all the substance melts or boils.
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संबंधित प्रश्न
Describe an experiment to demonstrate that water absorbs heat during boiling at a constant temperature.
State the boiling point of water.
A certain quantity of water is heated from 20°C to 100°C. Its temperature is recorded after each 1 minute. The observations are:
| Time (in minute) | Temperature (in °C) |
| 0 | 20 |
| 1 | 30 |
| 2 | 40 |
| 3 | 50 |
| 4 | 60 |
| 5 | 70 |
| 6 | 80 |
| 7 | 90 |
| 8 | 100 |
| 9 | 100 |
| 10 | 100 |
| 11 | 100 |
| 12 | 100 |
The boiling point of water is defined as ______.
Boiling of egg results in ______ change.
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.
Conversion of solid to vapour is called sublimation. Name the term used to denote the conversion of vapour to solid.
We would have observed that the plate that covers the cooked food items has water droplets inside. Why? Explain.
Assertion (A): Burning of a candle is considered a physical as well as chemical change.
Reason (R): Melting of wax is a physical change melted wax turns into vapours and then bums which is a chemical change.
Explain the terms boiling.
