question_answer 28)

Explain the following terms with an example each :                                    (a) Corrosion                                      (b) Rancidity                                                  

Answer:

(a) Corrosion : It is a process of deterioration of a metals as a result of its reaction with air orwater present in environment. Therefore, when metals are exposed to atmosphere, they react with air or water present in the environment and form undesirable compounds on their surfaces. This process is called corrosion . Almost all metals except noble metals such as gold, platinum and palladium get corroded. For example, when iron is exposed to moisture for a long time, its surface acquires a brown flaky substance called rust. Similarly, surface of copper acquires a green coating of basic copper carbonate, etc.                                            (b) Rancidity:  When fats and oils are exposed to air, they get oxidized and become rancid and their smell and colour change. This phenomenon is called rancidity To prevent rancidity of food materials containing fats and oils, certain substances (called antioxidants) are added which prevent oxidation and hence rancidity. Some food materials are stored in air tight containers or the bags containing the food materials (such as chips) are flushed with inert gas such as nitrogen to prevent them from getting oxidised.