How does water change states?

Hint: There are a total three states of water which can be converted into each other at particular temperature value. These values are called temperature of fusion when the solid form of water changes to the liquid form, similarly when liquid water changes to gaseous form it is called boiling temperature.

Complete step-by-step answer:
We know matter possesses three states, among these are solid, liquid and gaseous. These states are described on the basis of interatomic distance and force of attraction between the particles. When the interatomic distance is least and particles have most force of attraction then the state which forms is called solid state.

This state of water called as Ice and can be seen in your refrigerator it exist at $0{\,^ \circ }\,C$ , when temperature raise from $0{\,^ \circ }\,C$ onwards the force of attraction between the particles starts decreasing and the interatomic distance starts increases, at certain temperature rage we get another state of water called as liquid phase which you see normally as rain, tap water etc.
${H_2}O\,(s)\, \to \,{H_2}O(l)$

Now to change the liquid state into gaseous form, the temperature increases and liquid water starts boiling at $100{\,^ \circ }\,C$ we get to know about the third state of water which is gaseous form. Here $0{\,^ \circ }\,C$ is the freezing point while $100{\,^ \circ }\,C$ is the boiling point of water.
${H_2}O\,(l)\, \to \,{H_2}O(g)$

Note: When the state of water changes from liquid to gas two phenomena take place which are totally different. These are evaporation processes and boiling, boiling happens when temperature of vapors of liquid becomes equals to the atmospheric pressure. While evaporation is a surface phenomenon.