Explain the changing states of matter by taking the example of water.

Water exists in three states i.e., ice (solid), water (liquid), and steam (gas) and it changes from one state to another when heat is added or removed.

1. Solid to liquid
   Ice is the solid form of water and when heated, it absorbs heat energy which makes the molecules move faster and break free from their fixed positions and hence, melts into liquid water. This complete process is called melting.

2. Liquid to gas
   When water is heated, its particles move even faster and at boiling point it changes into steam (gas form).

3. Gas to Liquid
   When steam or water vapour is cooled, particles lose energy and come closer together to form water (liquid). This process is called condensation.

4. Liquid to Solid
   When water is cooled, its molecules slow down and arrange into a fixed position which is known as freezing process and thus, liquid water changes into ice.