$(a)$ 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?

$CO_{2}$ is a gas. Write any two of its gaseous properties to justify this. How can we liquefy this gas? Solid $CO_{2}$ is also known as dry ice. Why?

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

Comment upon the following: Rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy, and density.

Which phenomenon occurs during the following changes?
$(a)$ Formation of clouds.
$(b)$ Drying of wet clothes.
$(c)$ Wax melts in the sun.
$(d)$ Size of naphthalene balls decreases.

Fill in the blanks :
$(a)$ Evaporation of a liquid at room temperature leads to a ........... effect.
$(b)$ At room temperature,the forces of attraction between the particles of solid substances are ........... than those which exist in the gaseous state.
$(c)$ The arrangement of particles is less ordered in the ........... state. However,there is no order in the ........... state.
$(d)$ ........... is the change of solid state directly to vapour state without going through the ........... state.
$(e)$ The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called ...........