Rigidity : Property by which an object retains its shape and size is called as rigidity.

Solids are rigid whereas liquids and gases are not.

Compressibility : Compressibility is the property; due to which a substance can be compressed, means its volume can be decreased. Gases are compressible whereas solids and liquids are not.

Fluidity : Flowing tendency of a substance called fluidity. Gases and liquids are fluids, solids are not.

Filling a gas container : a large volume of gas can be filled in a gas container by compressing it under very high pressure. The property of compressibility (of gases) ivey sue full in this case

Shape : The property of having a definite geometry is called shape of a particular substance. Solids have a definite shape whereas gases and liquids do not have.

Kinetic energy : The energy possessed by a moving object or by the moving molecules of called kinetic energy.

On increasing the temperature, kinetic energy of a substance (or its molecules) also increases. Molecules of gases posses highest kinetic energy.

Density : The mass per unit volume of a substance is called density.

Density $=$ $\frac {\rm {Mass}}{\rm {Volume}}$