(i) Rancidity: Fat and oil containing food when kept open in air gets oxidised and become rancid due to which the taste and smell of food changes.
(ii) Two methods to reduce rancidity are keep the food in closed containers and use antioxidants.
(iii) Corrosion is seen in metals, when kept exposed to form a layer of compound by reaction of metal with moisture, acid or gases present in it. Rusting is the process in which iron metal reacts with air and moisture to form brownish flaky substance called rust.
