Most kids like you enjoy the sour taste of beverages like butter milk, lemon juice and orange juice. Have you ever wondered what gives these beverages their tangy taste? These liquids taste sour because they contain acids. The word acid comes from the Latin word ‘acere’ which means ‘sour’. The acids found in the liquids that we drink are natural acids.
Now, think about baking soda, the same white powder that your mother uses to bake cakes for you. If you put it in your mouth, you will spit it out immediately as it is bitter in taste. If you rub its solution between your fingers, it will feel soapy. Substances like baking soda which have a bitter taste and have a soap-like texture, are known as bases. A chemist named Svante Arrhenius was the first person to define acids and bases, in 1887.
Most liquids are either acidic or basic in nature. However, we cannot possibly taste each and every substance to tell whether it is an acid or a base, can we? So, we use special type of substances to find out whether a substance is acidic or basic in nature. These substances are known as indicators.
Indicators change their colour when they are dipped into a solution containing an acidic or a basic substance. Litmus, turmeric and China rose petals are some of the naturally occurring indicators.
The most commonly used natural indicator is litmus. It is extracted from lichens. It has a purple colour, but when an acidic solution touches it, it turns red and when a basic solution touches it, it turns blue. Litmus is available in the market in the form of a solution or paper strips.
Acids, bases and the pH scale
Acids are molecules that split apart in water and release hydrogen ions. Think about hydrochloric acid (HCl). When HCl is added to water, it splits into H (+) (hydrogen ions) and Cl (–) (chlorine ions). It increases the number of hydrogen ions in the solution.
Bases are molecules that split when put in water and release hydroxide ions. Sodium hydroxide (NaOH) is a base. When NaOH is put into water, it splits apart into Na (+) (sodium ions) and OH (–) (hydroxide ions). The hydroxide ions can combine with hydrogen ions in the water and reduce the number of hydrogen ions in the solution.
The pH scale
Whether a liquid is an acid or a base in nature, depends on the type of ions in it. If a liquid has more hydrogen ions in it, then it is an acid, and if it has more hydroxide ions in it, then it is a base. The term pH tells us about the hydrogen ion concentration in a solution.
The pH scale goes from 1–14. The liquids having a pH value between 0 to 7 are acids, with 0 being the strongest acid. The liquids having pH values between 7 to 14 are bases with 14 being the strongest base.
If a liquid has a pH of 7, it is called neutral. The amount of hydrogen ions and hydroxide ions in a solution are equal. Water has a pH of 7 because when water breaks up, it splits into an equal amount of hydrogen and hydroxide ions.
Strong Acids and Bases
Just like the acids with a low pH of around 1 are highly reactive and dangerous, the bases with a high pH near 13 are very reactive and dangerous. Some of these chemicals are also available in your school chemistry lab. You must never handle acids or bases yourself unless supervised by your teacher. They are corrosive in nature and can burn your skin, so better be safe than sorry!
Acids and Bases in Nature
There are many strong acids and bases found in nature. Some of them are dangerous and are used as poisons by insects and animals. Some are helpful. Many plants have acids and bases hidden in their parts like leaves, thorns, seeds, or sap.
In our bodies
Our stomach uses hydrochloric acid to digest food and for killing harmful germs that can cause diseases. Lactic acid is produced in our muscles when we exercise. Our pancreas is basic in nature with a pH of 8- 8.1 and helps with digestion.
Sometimes people complain of having acidity in their stomachs because of overeating and they take antacid tablets or syrups to feel better. The antacids are basic in nature. When an acidic solution is mixed with a basic solution, the effect of both is neutralized. This reaction between the acids and bases is known as neutralization reaction. In such reactions, salt and water are produced and heat is evolved.
Acid +Base= Water + Salt
So, bases and acids work in sync to help our bodies function properly.
Acids and bases are often used in science and technology. The batteries of cars and invertors contain a strong acid called sulphuric acid. Bases are used in manufacturing household cleaning products, baking soda, and as fertilizers for crops.
Since acids and bases help neutralise each other, industrial units take advantage of this neutralization reaction to neutralize their acidic wastes before discharging them into the environment.
- Proteins are made up of amino acids.
- Vitamin C is also an acid called ascorbic acid.
- Ammonia is a base chemical.
- The sting of an ant contains formic acid. The effect of the sting can be neutralized by rubbing baking soda solution on it.
- Every cell of a human body contains an acid known as Deoxyribonucleic acid (DNA) that carries genetic information.
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