pH plays a very important role in everyday life - (i) pH in Humans and Animals, (ii) Acid Rain, (iii) pH in Plants, (iv) Digestive System, (v) Self Defence of Animals and Plants, and (vi) Tooth Decay.
Most of the biochemical reactions taking place in our body are in a narrow pH range of 7.0 to 7.8. Even a small change in pH disturbs these processes.
When the pH of rain water falls below 5.6, it is called acid rain. When acid rain flows into rivers, the pH of the river water also falls and it become acidic. As a result, the survival of aquatic life become difficult.
Plants have a healthy growth only when the soil has a specific pH range which should be neither highly alkaline nor highly acidic.
Stomach produces hydrochloric acid which helps in digestion of food. When we eat spicy food, stomach produces too much of acid which causes acidity - irritation and sometimes pain too. To get rid of this we use antacids which are bases like milk of magnesia (suspension of magnesium hydroxide in water).
Bee sting causes severe pain and burning sensation. It is due to the presence of methanoic acid in it. Use of a mild base like baking soda can provides relief from pain.
Some plants like nettle plant have fine stinging hair which inject methanoic acid into the body of any animal or human being that comes in its contact. This causes severe pain and burning sensation. The leaves of dock plant that grows near the nettle plant when rubbed on the affected area provides relief.
Tooth enamel is made of calcium phosphate which is the hardest substance in our body and can withstand the effect of various food that we eat. If mouth is not washed properly after every meal, the food particles and sugar remaining in the mouth undergoes degradation due to the bacterial present in the mouth. This process produces acids and the pH goes below 5.5. The acidic condition thus created corrode the tooth enamel and in the long run can result in tooth decay.