As chemistry students, we usually talk about pH when using universal indicator in the lab to determine the pH of certain substances but in reality we are exposed to pH on a daily bases.Before we understand how pH affects our lives, it is vital to understand the meaning of this term. The ‘potential of Hydrogen’ (pH) is a measure of hydrogen ion concentration; it is the measure of the acidity or alkalinity of a solution. This pH value is shown on a scale that usually ranges from 0-14, with 7 as the neutral number. Fig 1.1 shows a pH scale and the different pH levels in items we use daily. Items below 7 are acidic whereas items above 7 are alkaline.pH is very important to the biological systems. A change in pH could easily kill microorganisms or stop enzymes from working. Let us look deeply into the effects of the change in pH on our human body.Firstly, the pH of our mouth itself is extremely important. Tooth enamel is the hardest substance in our body. It is made up of calcium tetraoxophosphate (V). It does not dissolve in water and mildly acidic solutions. When we eat food-containing sugar, some food particles remain sticking to the teeth. The bacteria present in the mouth produces acid by the degradation of sugar and food particles present in the mouth (for example, lactic acid is produced). This causes the acid to form in our mouth after the sugary substance has been eaten. As a result of the acid produced, the pH in our mouth is lowered. If the pH goes below 5.5 then the tooth corrodes causing tooth decay. This is because the acid has become strong to affect the enamel of the tooth. As saliva is slightly alkaline, it is able to neutralise some of the acid, but the excess acid remains. The best way to prevent this is to clean the mouth thoroughly after eating food. Using toothpaste, which is generally basic, for cleaning the teeth can neutralize the excess acid and prevent tooth decay. Thus, we should avoid eating sugary food so that tooth decay can be prevented.Not only does pH play a pivotal role in the mouth but it is equally important in the digestive system. The medium in our stomach is highly acidic and has pH around 1.2. Our stomach produces hydrochloric acid. This dilute hydrochloric acid helps in digesting our food without harming the stomach. But if excess acid is produced in the stomach (e.g. Due to overeating) then it causes indigestion. This indigestion produces pain and irritation in the stomach as a result. It can also cause ulcers in the digestive system. The condition of excess acid in the stomach is referred to as hyperacidity. Neutralising the excess acid usually cures this pain. This is done by taking in bases known as antacids. The two common antacids used for curing indigestion due to acidity are Magnesium hydroxide (Milk of Magnesia) and Sodium hydrogen carbonate. Milk of Magnesia contains a mild base of magnesium hydroxide as the active component that neutralizes the excess acid in the stomach and thus controls the pH in the stomach. The reaction is shown below.Mg(OH)2 + 2HCl à MgCl2 + 2H2OThus, it is extremely important to keep a balanced diet with more alkaline food and less acidic food to prevent tooth decay and indigestion in our body.