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Answer :

Ice at 273K is more effective in cooling than water at the same temperature because between water particles and ice particles at the same temperature i.e., 273K or 0°C , ice particles have comparatively less heat energy(or kinetic energy) than water particles. Hence when ice is used to cool any object(which is to be cooled), then there is formation of energy gradient in which ice has less heat energy than the object, so heat energy flows from the object to the ice (energy flows from higher potential to lower potential) and as a result that object cools down. In case of water there will be cooling of the object but it will not be as effective as ice.

- Convert the following temperature to Celsius scale. (a) 293K (b) 470K
- Convert the following temperatures to the Kelvin scale. (a) \( 25°C \) (b) \( 373°C \)
- Give reason for the following observations: (a) Naphthalene balls disappear with time without leaving any solid. (b) We can get the smell of perfume while sitting several metres away.
- Arrange the following in increasing order of forces of attraction between the particles – water, sugar, oxygen.
- What is the physical state of water at – (a) 25°C (b) 0°C (c) 100°C?
- Give two reasons to justify – (a) Water at room temperature is a liquid. (b) An iron almirah is a solid at room temperature.
- What produces more severe burns, boiling water or steam?
- Name A, B, C, D, E and F in the following diagram showing a change in its state.

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