Question

Describe two changes that are harmful. Explain why you consider them harmful .How can you prevent them ?

Answer 1

Two changes which are harmful are:
1) Rusting of iron - it can cause damage to ships - can be prevented by galvanizing.
2) Food getting spoilt - it can cause food poisoning and other stomach related diseases - can be prevented by refrigerating

Answer 2

The two chemical changes which are harmful to us are given below:

1. Rusting on metal objects as it deteriorates the metal surface and decreases the efficiency of it.
2. Rancidity of food items which spoil the foodstuff as it is an oxidation process of food items that spoil the food permanently.

We can prevent these changes by following steps,

1. Rusting can be prevented by painting.
2. Rancidity can be stopped by addition of anti-oxidation like citric acid in food.