When we step barefoot into an office with a marble floor, we feel cold. Why?

1

(a)

This is because marble is a better conductor of heat than concrete. When we walk barefooted on a marble floor, heat flows our body through the feet and we feel cold.

Is it possible to convert water into vapour form without increasing its temperature, if temperature and pressure of water are \(30^{ 0 }\) C and 1 atm respectively?

1

(a)

yes, water at \(30^{ 0 }\) C can be converted into vapour by reducing its pressure until it equals to the vapour pressure of water at \(30^{0}C.\)

A tightened glass stopper can be taken out easily by pouring hot water around the neck of the bottle. Why?

1

(a)

The neck expands but not the stopper due to poor conductivity of glass. Thus, the stopper can be taken out easily.

Calorimeters are made of metals not glass. Why?

1

(a)

This is because metals are good conductors of heat and have low specific heat capacity.

Which object will cool faster when kept in open air, the one at 300 \(^{0}\) C or the one of 100 \(^{0}\)C? Why?

1

(a)

The object at 300 \(^{0}\)C will cool faster than the object at 100 \(^{0}\)C. This is in accordance with Newton’s law of cooling. As we know, rate cooling of an object \(\alpha \)  temperature between the object and its surroundings.