Anything that occupies space and has weight is called matter. Matter is made up of tiny particles called molecules. Molecules are made up of even smaller particles called atoms. All things or objects are matter.

Amount of space a matter takes is known as volume. Solids and liquids have a definite volume, but gases do not have a definite volume.

The process of changing a liquid into a solid on cooling is known as freezing. For example, water changes into ice on cooling.

The solution is a mixture of a solute and a solvent. Solutions can be of three types, solid-liquid, liquid-liquid and gas-liquid. When a solute is dissolved in a solvent the volume of the solvent does not increase.