1)water present in pot are cold .why?

2)why pigs roll themselves in mire?

3)when a bowl of water is placed in a closed container and the
water vapour is pumped away rapidly enough,why does the remaining liquid turns
into ice?

4)why does temperature of water decrease when mixed with with



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1. Water in a pot and the wet portion of a pot are colder than room temperature. This is due to the evaporation of water. Water seeps through the small pores of the pot to the outside and evaporates easily due to the low pressure in that region. The latent heat of evaporation is taken from the water in the pot and the earthen pot material.  So they become cooler.

2)  Pigs roll in mud water to cool themselves. Usually above 20 deg. they feel the heat. Pigs do not have the sweat glands like human beings to cool the skin.  So to cool their skin, they roll in wet mud. This is called wallowing in mud.   They cover their face and other parts of the body with wet mud.  Also, the mud protects them from direct Sun rays.  When they feel comfortable they shake of the mud or they wait until mud is dried and then rub against a wall or a post to remove it.

3) same reason as in question 1. When you pump out the water vapour, the pressure of air above water surface decreases.  Due to low pressure the boiling point of water reduces from 100 deg to 50 or 60 deg or even lower.  The latent heat required to become vapour is taken from the remaining water in the bowl and the bowl itself.  So they cool down.  When the actions happen rapidly, and a lot of heat is taken away, the water freezes giving out heat to the water molecules becoming vapour.


Glucose for example C6 H12 O6 is readily soluble in water. The glucose solid has an unstable open ring structure. In water the molecules of glucose are separated to greater distances by water molecules.  Also, the ring structure of glucose changes in to other isomers of glucose. The isomers have same molecular formula but have different structure and bonds between atoms in the molecule.

Thus dissolving glucose involves an endothermic reaction.  Heat is absorbed by the molecules of glucose during dissolution.  The heat is supplied by the water molecules. So water becomes colder.

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