Which term is used to indicate the development of unpleasant smell and taste in fat and oil containing foods due to aerial oxidation (when they are kept exposed for a considerable time)?

3 Why does the colour of copper sulphate solution change when an iron nail is kept immersed in it ? 4 Write the balanced chemical equation for the following reaction :

Zinc + Silver nitrate Zinc nitrate + Silver

6 What is the general name of the chemicals which are added to fat and oil containing foods to prevent the development of rancidity? 7 State an important use of decomposition reactions.