(a) The differences in the characteristics of states of matter are given in the following table.
||Definite shape and volume.
||No definite shape. Liquids attain the shape of the vessel in which they are kept.
||Gases have neither a definite shape nor a definite volume.|
||Compressible to a small extent.
||There is little space between the particles of a solid.
||These particles have a greater space between them.
||The space between gas particles is the greatest.|
||These particles attract each other very strongly.
||The force of attraction between liquid particles is less than solid particles.
||The force of attraction is least between gaseous particles.|
||Particles of solid cannot move freely.
||These particles move freely.
||Gaseous particles are in a continuous, random motion.|
(b) (i) Rigidity: The property due to which an object retains its shape and size is known as rigidity. Solids are rigid whereas liquids and gases are not.
(ii) Compressibility is the property due to which a substance can be compressed, i.e., its volume can be decreased. Gases are compressible whereas solids and liquids are not.
(iii) Fluidity: The property due to which a substance tends to flow is called fluidity. Gases and liquids are fluids, solids are not.
(iv) Filling a gas container: A gas can be filled in a gas container by compressing it under high pressure. The property of compressibility (of gases) helps them in this regard.
(v) 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.
(vi) Kinetic energy: The energy possessed by an object or by the molecules of an object due to its state of motion is called kinetic energy. Molecules of gases posses highest kinetic energy. Increasing the temperature also increases the kinetic energy of a substance (or its molecules).
(vii) Density: The mass per unit volume of a substance is called density.