$(a)$ Define boiling point.
$(b)$ Express the boiling point of water in Celsius as well as Kelvin scale.
$(c)$ $A$ diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

Define the following terms: $(i)$ Rigidity,$(ii)$ Compressibility,and $(iii)$ Density. Compare any two states of matter on the basis of the above-defined properties.

In which of the following conditions,the distance between the molecules of hydrogen gas would increase?
$(i)$ Increasing pressure on hydrogen contained in a closed container
$(ii)$ Some hydrogen gas leaking out of the container
$(iii)$ Increasing the volume of the container of hydrogen gas
$(iv)$ Adding more hydrogen gas to the container without increasing the volume of the container

$(a)$ What is matter? Write two properties of solids and two properties of liquids.
$(b)$ Ramesh took two beakers $A$ and $B$ containing hot water and cold water respectively. In each beaker,he dropped a crystal of copper sulphate. He kept the beakers undisturbed. After some time,what did he observe? Why?

Explain:
$(a)$ Sponge,though compressible,is a solid.
$(b)$ Gases completely fill the vessel in which they are kept.

Give reasons for the following:
$(i)$ $A$ liquid generally flows easily.
$(ii)$ Ice at $0^{\circ} C$ appears colder to the mouth than water at $0^{\circ} C$. Why?
$(iii)$ Doctors advise putting strips of wet cloth on the forehead of a person having a high temperature.