Chemical change
For example, burning of magnesium, rusting iron, preparation of gases in the laboratory, etc.
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
 |
| Ice melting: an example of 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, melting of ice, distillation of water, magnetising a needle, etc.
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.
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. |
No comments:
Post a Comment