Question

Following are the observations of changes that have taken place. Classify them into chemical change or a physical change. [5 MARKS]

1. The change is temporary and can be reversed by changing the conditions in most of the cases.
2. New substance(s) is/are formed.
3. The chemical properties of the original substance remain the same.
4. There is an exchange of energy during this change which means that heat and light may be given out or absorbed.
5. As a result of the change, there may or may not be any change in the energy possessed by the original substance.
6. There is no change in the chemical composition of the original substance.
7. The change is permanent and cannot be reversed by changing the conditions or through ordinary physical processes.
8. There may or may not be any change in the state, size, shape, colour, and smell of the substance that undergoes this change.
9. The composition and the properties of the parent substance or substances change.
10. There is usually a change in the mass of the parent substance/s as well.

Answer 1

Classification: 0.5 Mark each

Physical Change:
1. There is no change in the chemical composition of the original substance.
2. The change is temporary and can be reversed by changing the conditions in most of the cases.
3. The chemical properties of the original substance remain the same.
4. There may or may not be any change in the state, size, shape, colour, and smell of the substance that undergoes this change.
5. As a result of the change, there may or may not be any change in the energy possessed by the original substance.

Chemical change
1. New substance(s) is/are formed.
2. The composition and the properties of the parent substance or substances change.
3. The change is permanent and cannot be reversed by changing the conditions or through ordinary physical processes.
4. There is an exchange of energy during this change, which means that heat and light may be given out or absorbed.
5. There is usually a change in the mass of the of the parent substance/s as well.