How do the following help in bringing about a chemical change? Explain each with a suitable example.

(a) Pressure

(b) Light

(c) Catalyst

(d) Heat

(a) Define catalyst.

(b) What are (i) positive catalysts and (ii) negative catalysts? Support your answer with one example for each of them.

(c) Name three biochemical catalysts found in the human body.

What do you observe when a few pieces of iron are dropped in a blue solution of copper sulphate?

What do you observe when silver nitrate is added to a solution of sodium chloride?