4. Give reasons :
i) A sponge can be pressed easily; still it is called a solid.
ii) Water vapours have more energy than water at same temperature
Answers
Explanation:
sponge is a porous solid. 2. It is because water vapour being a gas exerts much more pressure than waterwhich is a liquid at the same temperature. water is heated it turns to gaseous vapour and the steam gives of a hot heat gas , when we put at high pressure it gives more energy
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Answer:
(i) This is because it has air pores present inside it which are filled with air, so when it is pressed the air rushes out of the pores. But until it is not pressed , it retains its original shape. Therefore , a sponge is a solid.
(ii) Water vapour have more energy than water in the same temperature because the water vapour have latent heat of vapourization which has more heat energy, whereas the water at the same temperature do not have latent heat as it need latent heat to change in state but the water vapour already had it, it needs to release that latent heat to change its state. That's why , water vapour have more energy and is more effective in burning skin.
(iii) Evaporation is the process of conversion of liquid state into gaseous state before it's boiling point. Evaporation is a bulk phenomenon. It occurs at any temperature below the boiling point.
Evaporation depends upon - surface area, nature of liquid, amount of humidity, speed of wind , temperature of the environment.
(iii) Evaporation causes cooling as the the liquid takes up the latent heat from the surface to change its state from liquid to gass. As it takes up heat, this causes cooling effect.
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