physical and chemical changes

Physical and Chemical change

Chemical change

A chemical change is more or less permanent and gives rise to a new substance having composition and properties altogether different from those of the original substances.
For examples of chemical change, burning of magnesium, rusting iron, preparation of gases in the laboratory, etc.
chemical change

Burning of paper

Experiment

Take a little sugar in a test tube. Heat test tube slowly for sometime. You will see that sugar turns into black and some water droplets collect on its mouth. Sugar turns into carbon and water due to heat. Such a change is known as Chemical change.

Physical Change

A physical change is change of state only and is not accompanied by an alternation in composition, weight or chemical properties of substances. Examples of physical changes, melting of ice, distillation of water, magnetism a needle, etc.

physical change

Melting of ice

Experiment

Take some water in a beaker. Put a watch glass on its mouth containing some water. Heat the beaker as shown in the figure. You will see that water vaporizes. Some water droplets will be seen on the inner side of water glass. This is due to water in the watch glass. Thus, when water is heated it turns into vapour and after cooling, again, it turns into water. Such a change is known as Physical change.
 From above discussion we come to conclude that chemical change cannot be reversed and physical change can be reserved.

There are certain distinctions in between physical change and chemical change. The points of difference between physical and chemical changes are summarized in the table below.

Difference between physical and chemical changes:

           
Chemical change
Physical change
1. Change takes place in the composition of the  substance.
1. No alternation in the chemical composition.
2. A new substance is formed with entirely different properties.
2. The chemical properties remain the same. A change may take place only in some of the  physical properties like color, taste, etc.
3. The chemical can’t be reversed and is permanent.
3. The change is temporary and can be easily reversed back.
           
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