In an exam, a teacher asked students to give an example of a change which is a physical as well as a chemical change? Which one of the following examples is correct?
In an exam, a teacher asked students to give an example of a change which is a physical as well as a chemical change? Which one of the following examples is correct?
The correct option is B Burning of candle
Among the given examples only burning of a candle involves both physical as well as chemical change. It is a physical change because, on heating, the candle wax melts and it again turns into solid wax on cooling down a little. It is a chemical change because, the wax near to the flame, on burning, gives rise to new substances like carbon dioxide, carbon soot, water vapour, heat and light.
Photosynthesis is a chemical change. It involves the formation of a new substance (glucose).
Beating of aluminium to make foil and dissolving salt in water is are both physical changes because in both the processes no new substance is formed. For instance, aluminium will show the same set of chemical properties even if it has been turned into a foil.
Burning of candle
Among the given examples only burning of a candle involves both physical as well as chemical change. It is a physical change because, on heating, the candle wax melts and it again turns into solid wax on cooling down a little. It is a chemical change because, the wax near to the flame, on burning, gives rise to new substances like carbon dioxide, carbon soot, water vapour, heat and light.
Photosynthesis is a chemical change. It involves the formation of a new substance (glucose).
Beating of aluminium to make foil and dissolving salt in water is are both physical changes because in both the processes no new substance is formed. For instance, aluminium will show the same set of chemical properties even if it has been turned into a foil.
