Chemical Change

Changes occur every minute, every second of the day.

There is a change when we fold a paper, cut it, burn it or when we boil an egg.

Broadly, all changes can be classified as physical or chemical.

In this story, we will discuss the chemical changes.

A chemical change is a change in which new substances are formed.

For examples when a paper is burnt it produces carbon dioxide and water vapour, which are nothing like paper.

They are entirely new substances. It is thus a chemical change.

Apart from the formation of new substances, a chemical change involves other changes too.

Changes such as:1. Production of heat and light 2. A change in smell3. Change in colour4. Evolution of gas 5. Production of sound

1. Magnesium ribbon burns in air to produce heat and light.

It burns with oxygen in the air to form a new substance, magnesium oxide.

Magnesium oxide dissolves in water to produce magnesium hydroxide- a new substance.

2. A solution of magnesium hydroxide brings about a change in colour to litmus paper.

It turns red litmus paper blue, which can not be reversed.

It occurs due to the formation of a new substance when litmus interacts with magnesium hydroxide, thus a chemical change.

When Copper sulphate solution reacts with iron nails it too produces a change in colour.

The change in colour is due to the formation of a new substance, iron sulphate, which is green.

There is also a brown deposit on the iron nail, which is of copper.

3. When a mango ripens it produces a change in colour as well as smell.

Raw fruits have a green pigment called chlorophyll.

During ripening, a change occurs in which green pigment changes to new pigments-red and yellow.

This change in the pigments brings about the change in the smell of the ripe mangoes.

4. The reaction between vinegar and baking soda takes place with the evolution of gas.

The gas produced in the reaction is carbon dioxide.

The gas produced can be identified if it turns lime water milky.

The milky appearance is due to the formation of another new substance calcium carbonate.

5. Firecrackers burn with a deafening sound along with the production of heat and light.

Once the firecrackers burn, the substances formed are nothing like the substances we started with. Thus, it is a chemical change.

Revision

All changes can broadly be classified as physical or chemical.

A chemical change is a change in which new substances are formed.

A chemical change is accompanied by:1. Production of heat and light 2. A change in smell3. Change in colour4. Evolution of gas 5. Production of sound

The end