Write the difference between order and molecularity of reaction.

Explanation

### Step-by-Step Solution

1. **Definition of Order of Reaction**:
- The order of a reaction is defined as the sum of the powers of the concentration terms in the rate law expression. It is an experimentally determined value that reflects how the rate of reaction depends on the concentration of reactants.

2. **Definition of Molecularity of Reaction**:
- Molecularity refers to the total number of reacting species (atoms, molecules, or ions) that collide in an elementary reaction. It is a theoretical concept that indicates the number of particles involved in the reaction mechanism.

...