Complete the following statements.

(a) The chemical change involving iron and hydrochloric acid illustrates a …………… reaction.

(b) In the type of reaction called …………… two compounds exchange their positive and negative radicals.

(c) A catalyst either …………… or …………… the rate of a chemical change but itself remains …………… at the end of the reaction.

(d) On heating, hydrated copper sulphate changes its colour from …………… to ……………

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.

(a) What is synthesis?

(b) What kind of chemical reaction is synthesis? Support your answer with an example.

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