When hydrogen burns in oxygen, water is formed; when electricity is passed through water, hydrogen and oxygen are given out. Name the type of chemical changes involved in the two cases.

Explain the following chemical changes by giving one example of each:

(a) Double decomposition

(b) Thermal dissociation

(c) Reversible reaction

(d) Displacement

Decomposition brought about by heat is known as thermal decomposition. What is the difference between thermal dissociation and thermal decomposition?

(a) What is a decomposition reaction ?

(b) Decomposition reactions can occur by (i) heat (ii) electricity and (iii) sunlight.
Give two balanced reactions for each.