What are chemical reaction

Example:-

We cannot pull back the reaction to get wax back .

Explanation:

The permanent change in which a new substance is formed is called a chemical reaction.

For example:

i)Burning of wood

ii)Cooking rice

iii)Forming curd from milk

The burning of wood is a chemical reaction because it is a permanent change and it cannot be reversed. Once it is done, it is over it can't be done again. And in the case of example iii, the milk turns into curd by chemical reaction. A new substance i.e curd is formed from the milk.

Hope you understood!