A tightnened glass stopper can be taken out easily by pouring hot water around the nect of the bottle. Why it is so?

We can easily boil water in a paper cup. Why?

A tightly closed metal lid of a glss bottle can be opened more easily if it is put in hot water for some time. Expoain.

A bottle is full of dettol .One third if it , is taken out and then equal amount of water is poured into the bottle to fill it .This operation is done four times .Find the final ratio of dettol and water in the bottle .

Paheli had bought a new bottle of pickle from the market. She tried to open the metal cap to taste it but could not do so. She then took a bowl of hot water and immersed the upper end of the bottle in it for five minutes. She could easily open the bottle now. Can you give the reason for this?

In order to loosen a stopper from the neck of a glass bottle, boiling water is poured around the neck. Why?

A large bottle is fitted with a siphon made of capillary glass tubing. Compare the times taken to empty the bottle when it is filled. (i) with water (ii) with petrol of density 0.8 cgs units. The viscosity of water and petrol are 0.1 and 0.2 cgs units repectively.