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Answers
1. The term latent heat of vaporisation can be defined as the amount of heat needed for the conversion of 1kg of liquid at its boiling point to gas at same temperature. It differs among different liquids.
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2. The temperature remains constant during the change of state because the heat energy which is supplied to change the state of matter is used in breaking the intermolecular forces and other attractive forces. Hence the temperature remains constant as all the heat is used up and no external heat is released or absorbed.
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3. Sublimation is a chemical process where a solid turns into a gas without going through a liquid stage. ... An example of sublimiation is when ice cubes shrink in the freezer.
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4. On dry days, sweat evaporates quickly, which means it also carries away heat faster. On humid days, when the air is already saturated with water, sweat evaporates more slowly. This explains why it feels so much hotter in high humidity.
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5. Condensation can also produce water droplets on the outside of soda cans or glasses of cold water. When warm air hits the cold surface, it reaches its dew point and condenses. This leaves droplets of water on the glass or can.
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6. kelvin =273
(a) 25°C= 25 + 273 = 298k
(b) 373°C= 373+273=646K
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7. Both solids and liquids have a fixed volume, and also both of them are in compressible and secondly, both have high density
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8. (i) Gases and liquids do not have fixed shape. (b) The shape does not change when pressed i.e. it is hard and rigid. It has a definite shape and has high density.
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9. The melting point of ice will decrease is some common salt is added to it. This is because addition of non- volatile solute(salt) causes a depression in the freezing point of water. Due to this water freezes at a lower temperature and thus ice starts melting at a faster rate.
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10. You can indicate that air has utmost compressibility by making use of 3 syringes with one sealed with water and other with air and hence other with chalk whereas the one with air will let compression to the maximum degree compared with the others.