A cell of a unicellular organism is in direct contact with the environment and intake of oxygen occurs directly by diffusion. While Many cells of multi-cellular organisms like human are not in contact with the external environment.
Procedure: The question ask for heating lead nitrate into a test tube filled with boiling water.
Observation: A yellow precipitate of lead oxide is formed with evolution of brown nitrogen di oxide gas which has irritating smell
Decomposition of ferrous sulphate into ferric oxide by heating.
Quick lime reaction with water.