Question

(a) Explain the pH change as the cause of tooth decay. How can tooth decay caused by pH change be prevented?
(b) Explain how pH change in the lake water can endanger the lives of aquatic animals (like fish). What can be done to lessen the danger to the lives of aquatic animals in the lake?

Answer 1

(a) When the pH of the mouth falls to around 5.5, tooth decay begins. As the acidity in the mouth increases, the acid reacts with the tooth enamel and causes tooth decay.
Tooth decay can be prevented by brushing with toothpastes (which are basic and neutralise the acid formed) regularly and by cleaning the mouth carefully after meals.

(b) Because of acid rain (when the pH of rainwater is 5.6), the acidity of river and lake water increases. Aquatic animals find it very difficult to survive in water with low pH levels, and they die.
To neutralise this excess acidity in lakes and rivers caused by acid rain, calcium carbonate, a base, is frequently mixed with the water.