A chemical change is the transformation of one material into another, resulting in new materials with different properties and one or more new substances. When we burn paper, it turns into ash. From this ash, we cannot get paperback. This is because the burning of paper is a chemical change.

Various types of changes can be seen occurring in the environment regularly. Some occur naturally, while human activities cause others to meet their needs. These changes can be classified into two types: physical and chemical change. To learn more about chemical change, read the below article.

Define Chemical Change

Those changes in which new substances are formed are called chemical changes. During a chemical change, a substance changes its chemical composition (or change in chemical properties). Chemical reactions are another term for chemical changes. Substances are converted into entirely new substances during a chemical change. In most cases, the new substances cannot be returned to their original form. This means that most chemical changes are irreversible.

Characteristics of Chemical Changes

The easily observable features of changes that take place as a result of chemical reactions are known as characteristics of chemical changes.

Thus, the various characteristics of a chemical change are as follows:

1. A chemical change results in the formation of one or more new substances: For example, When we burn a piece of paper with a lit match stick, then entirely new substances such as carbon dioxide, water vapour, smoke, and ash are produced. So, chemical change results in the formation of new substances.
2. A chemical change is a permanent change. A chemical change usually cannot be reversed: For example, burning paper is a permanent change that cannot be reversed. This is because we cannot recombine the by-products of paper burning to create the original paper.
3. A large amount of energy (in the form of heat, light, and sound) is either absorbed or released during a chemical change: The burning of a cracker causes a chemical change. When a cracker explodes, it emits heat and light energy, as well as sound. As a result, energy changes are involved in chemical changes.
4. A chemical change may cause a change in smell or the release of a new smell: When food gets spoiled, it produces a foul smell. This shows that new substances have been formed in spoiled food which has a foul smell.
5. A chemical change may result in a permanent colour change: Fruit ripening is a chemical change. The colour of raw fruit changes as it ripens.
6. A gas can be formed as a result of a chemical change: A chemical change occurs when a metal, such as zinc, reacts with dilute hydrochloric acid, as a salt called zinc chloride is formed and a gas called hydrogen is evolved.

Examples of Chemical Change

Some examples of chemical changes are as follows:

1. During photosynthesis, the plants combine carbon dioxide and water in the presence of chlorophyll and sunlight to form two new substances such as glucose and oxygen gas. So, photosynthesis is a chemical change.
2. The various food materials break down during digestion to form new substances that can be absorbed by the body.  So, the process of digestion is a chemical change.
3. When an acid reacts with a base, a neutralisation reaction occurs, resulting in the formation of two new substances, salt and water. As a result, neutralisation is a chemical change.
4. Anaerobic bacteria in a biogas plant digest (break down) animal wastes such as cow dung to produce biogas, the main component of which is methane gas. The synthesis of biogas from animal waste is a chemical process. This is due to the production of new substances such as methane from animal waste.
5. Burning of Magnesium ribbon: Magnesium is a metal that easily burns when heated. Magnesium ribbon is a long, thin strip of magnesium metal. To carry out activities, we usually use magnesium metal in the form of a magnesium ribbon. When a magnesium ribbon is heated, it burns in the air with a brilliant white light to form magnesium oxide, powdery ash. This magnesium oxide is an entirely new substance. As a result of the burning of the magnesium ribbon, a new substance is formed.  So, the burning of the magnesium ribbon is a chemical change.

6. The reaction between baking soda and vinegar: When baking soda and vinegar are combined, bubbles of carbon dioxide gas, as well as other substances are formed. Because carbon dioxide is formed as one of the new substances as a result of the reaction between baking soda and vinegar, it is said to be a chemical change.

\(\mathop {{\rm{Sodium}}{\mkern 1mu} \,{\rm{hydrogen}}\,{\rm{carbonate}}}\limits_{\left( {{\rm{Baking}}{\kern 1pt} {\rm{soda}}} \right)}  + \mathop {{\rm{Acetic}}\,{\mkern 1mu} {\rm{acid}}}\limits_{\left( {{\rm{Vinegar}}} \right)}  \to {\rm{Sodium}}\,{\mkern 1mu} {\rm{acetate  +  Carbon}}{\mkern 1mu} \,{\rm{dioxide  +  Water}}\)

7. The reaction between copper sulphate solution and iron: When an iron nail is immersed in a blue copper sulphate solution, a chemical reaction occurs, resulting in a green iron sulphate solution and a brown copper deposit on the iron nail.

\(\mathop {{\text{Copper}}\,{\text{sulphate}}\,{\text{solution}}}\limits_{\left( {{\text{Blue}}} \right)} {\text{ + }}\mathop {{\text{Iron}}}\limits_{\left( {{\text{Grey}}} \right)} \to \mathop {{\text{Iron}}\,{\text{sulphate}}\,{\text{solution}}}\limits_{\left( {{\text{Green}}} \right)} {\text{ + }}\mathop {{\text{Copper}}}\limits_{\left( {{\text{Brown}}} \right)} \)

The reaction between copper sulphate \((\rm{CuSO}_4)\) solution and iron \((\rm{Fe})\) is a chemical change because it produces two new substances such as iron sulphate \((\rm{FeSO}_4)\) solution and copper \((\rm{Cu})\).

Importance of Chemical Changes

In our daily lives, various types of chemical changes occur. Some are natural, while others are artificial. The majority of them are extremely beneficial to us. Some examples are as follows:

1. Raw grains are inedible, but when cooked, they change chemically and become edible.
2. Many useful metals, such as iron, aluminium, and copper, are extracted from their combined states through a variety of chemical processes.
3. Soaps, detergents, paints, fertilizers, medicines, etc., are all produced due to chemical changes.
4. The burning of fuel is a significant chemical change because it generates a large amount of heat energy, which is used for domestic and industrial purposes.
5. The various life processes that occur in plants and animals are all chemical changes that help to sustain life.
   For example,
   a. Food digestion is a process in which enzymes break down our food so that it can be absorbed in our bodies.
   b. Respiration is a chemical process that occurs in all living organisms. In this process, oxygen in the air is inhaled by living beings and reacts with digested food to produce energy, carbon dioxide, and water. This change cannot be reversed.
   c. \({\text{Glucose}} + {\text{Oxygen}} \to {\text{Carbon dioxide}} + {\text{Water}} + {\text{Energy}}\)

What is Physical Change?

Physical changes are those in which no new substances are formed. The substances involved in a physical change do not change their identity. Some physical processes can easily return to their original form. Physical changes can thus be easily reversed. The changes in physical state, size and shape of a substance are physical changes.

Some common examples of physical changes are: Melting of ice (to form water);zing of water (to form ice); Boiling of water (to form steam); Condensation of steam (to form water); Making a solution; Glowing of an electric bulb; and Breaking of a glass tumbler.

Difference between Physical Change and Chemical Change

The main differences between physical and chemical changes are as follows:

Physical Change	Chemical Change
1. A physical change does not result in the formation of a new substance.	1. A chemical change results in the formation of a new substance.
2. A physical change is temporary.	2. A chemical change is permanent.
3. A physical change is reversible in nature.	3. A chemical change is irreversible in nature.
4. In physical changes, very little heat energy (or light) is absorbed or released.	4. In a chemical reaction, a lot of heat (or light) energy is absorbed or released.
5. A physical change has no effect on the mass of a substance.	5. When a substance undergoes a chemical change, its mass changes.

Summary

Those changes in which new substances are formed are called chemical changes. During a chemical change, a substance changes its chemical composition. Physical changes are those in which no new substances are formed. The substances involved in a physical change do not change their identity. Chemical change results in the evolution of gas, change in colour and release or absorption of energy in the form of heat, light and sound.

FAQs

Q.1. What are \(5\) examples of a chemical change?
Ans: The five examples of chemical changes are rusting of iron, combustion, photosynthesis, ripening of fruits and curdling of milk.

Q.2. What is chemical change give example?
Ans: Those changes in which new substances are formed are called chemical changes. For example, burning of paper, cooking of food, burning of crackers, etc, are some examples of chemical change.

Q.3. What is a chemical change and a physical change?
Ans: The change in which no new substances are formed is called a physical change. The change in which new substances are formed is called a chemical change.

Q.4. What are \(3\) types of chemical changes?
Ans: The three types of chemical changes are Combination, decomposition and displacement reactions.

Q.5. Is chemical change reversible?
Ans: No, a chemical change is irreversible.

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