Let us recapitulate

1. In every chemical reaction, there is a chemical change.

2. In a chemical reaction, there is a rearrangement of atoms which takes place by breaking bonds in reactants and making new bonds in products.

3. Chemical reactions are classified into following types –(i) Combination (ii) Decomposition (iii) Double decomposition (iv) Neutralisation (v) Displacement (vi) Redox

4. In a combination reaction, a single substance is formed from two or more substances.

5. In a decomposition reaction, one substance splits into two or more sub- stances.

6. In a double decomposition reaction, mutual exchange of radicals takes place between two substances.

7. In a neutralization reaction, an acid and a base ( or alkali ) react to form salt and water.

8. In a displacement reaction, a more reactive element substitutes a less reactive element from its salt solution.

9. In a oxidation reaction, oxygen is added to a substance or hydrogen is removed from a substance. In a reduction reaction, oxygen is removed from a substance or hydrogen is added to a substance. Oxidation and reduction reactions take place at a time.

10. Every chemical reaction has its own rate which depends upon the na- ture of reactants, size of the particles, concentration of the substances, temperature, use of catalyst etc.

11. A catalyst increases the rate of the reaction. Many industrial processes use catalysts to increase their productions.