In 1909 Sorenson devised a scale known as pH scale on which the strength of acid solutions as well as basic solutions could be represented by making use of the hydrogen ion concentrations in them. He linked the hydrogen ion concentrations of acids and base solutions to the simple numbers 0 to 14 on the pH scale. Or we can say that the pH of a solution is inversely proportional to the concentration of hydrogen ions in it. That is, a solution having a high concentration of hydrogen ions has a low pH value. Whenever a solution has a pH value less than 7 then it is acidic and if more than 7 then it is basic. If the solution has 7 value then it is neither acidic nor basic.
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Therefore, we can say that the pH plays an important role in many activities of our everyday life. Like pH of gastric juices in the stomach is important in the process of digestion, the pH in mouth can become a cause of tooth decay etc. The plants and animals are sensitive to pH changes in their environment. Infact, to a large extent, the growth of plants and survival of animals depends upon the availability of proper pH conditions which suit them.
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Let us see how plants and animals are sensitive to pH Changes
A. Growth of Plant and pH of Soil
Do you know that most of the plants grow best when the pH of the soil is close to 7. If the soil is too acidic or too basic or alkaline then plants can’t grow at all. So, soil naturally should be acidic or basic. The pH of soil is also affected by the use of chemical fertilisers in the fields. The pH of acidic soil can reach as low as 4 and that of basic up to 8.3. Chemicals can be added in the soil to adjust its pH concentration and make it suitable for the plants to grow.
If the soil is too acidic then it is treated with the materials like quicklime or calcium oxide, slaked lime or calcium hydroxide or chalk i.e. calcium carbonate. All these are bases and hence react with the excess of acid present in the soil to reduce its acidity. Sometimes it may also happen when soil is too basic having pH value high. Then in this case the alkalinity if the soil can be reduced by adding decaying organic matter i.e. manure or compost which contains acidic materials.
B. Survival of animals and change of pH
Do you know that pH plays an important role in the survival of animals, including human beings? Our body works well within a narrow pH range of 7 to 7.8. If, due to some reason, this pH gets disturbed or change in the body of a person, then many ailments can occur. But the aquatic animals like fish can survive in lake or river water within a narrow range of pH change. For example when the pH of rain water is about 5.6 then it is acid rain. Too much acidic rain makes difficult for the aquatic animals to survive and can even kill the aquatic animals. In that case calcium carbonate is added to acidic lake water to neutralise the acid that comes from acid rain. This prevents the aquatic animals from being killed.
Also, acids are present on other planets too. For example, the atmosphere of planet Venus is made up of thick white and yellowish clouds of sulphuric acid. So, life cannot exist on the planet Venus.
Therefore, from the above article we come to know that pH plays an important role in the life of plants and animals to survive.