# Chemical Change: Reversible And Irreversible Changes

## What is a chemical change

Changes are very random or an uncertain phenomenon, it can be better or worse depending on your view. Every day we see different objects changing around us like melting of ice, cooking of food etc. In some cases, you get back the original substance and in some, you won’t get it back. Some changes are slow while some are fast, some are natural and some are man-made. You will find that many changes are taking place around us for e.g. growing of plants in your balcony, sometimes there is a change in colour and sometimes you will find drying of leaves.

#### Chemical Change Definition

A chemical change can be defined as a chemical reaction in which one or more substances undergo changes to form new substances or a new structure.

## Types of chemical change

Changes are mostly of two types

• Reversible change
• Irreversible change

### Reversible change

A reversible chemical reaction is a chemical reaction that can go in both directions; the reactants can change into the products, and the products can change back into the reactants. This happens continually until it reaches a point called equilibrium. That’s when the two reactions going in opposite directions happen at the same rate and there is no longer any change to the amount of reactant and product.

N2(g) + 3H2(g) $$\rightleftharpoons$$ 2NH3(g)

### Irreversible change

The change which is almost permanent and cannot be undone by any physical or chemical means is called an irreversible change. Some new substances are formed in the case of an irreversible change.

There are many advantages of reversible and irreversible changes. For example, a piece of iron is cast into different shapes by a blacksmith. It is beaten into the desired shape after it is heated. On heating, the metals expand while it contracts on cooling. By this, you can understand why there are small gaps left between the rails in railway lines. This is because the metal tracks expand in summers due to high temperature. Thus, these gaps compensate for the increase in area due to expansion.

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