(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?
(a) Tooth decay starts when the pH of the acid formed in the mouth falls below 5.5 because the acid becomes strong enough to attack the enamel of the teeth and corrode it.
(b) The pH of lake water becomes lower because of too much acid rain. The high acidity of lake water can kill the aquatic animals like fish since they can survive within a narrow range of pH change.
Calcium carbonate is added to acidic lake water to neutralise the acid and this prevents the fish from being killed.