explain with example how the physical state of reactants and products can be shown in chemical equation

In chemical equations, we usually state the state symbol behind each of the reactants and products. We use (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous solutions.

For example, here's an equation of sodium reacting with water:

2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)

As you can see, each behind each substance is the state symbol. This is how we presents physical states in chemical equations.