Question

Glowing of an electric bulb is _________ type of change.
A. Physical
B. Chemical
C. Both physical and chemical
D. None of these

Answer 1

Hint: Size, shape, colour and state are all physical properties of a substance. When an observable change is seen in these properties of a substance, we call it a physical change.

Complete step by step answer:
Change in state of matter, change is solubility, colour, odour are all considered as physical changes.
Composition or chemical nature of a substance does not change when it undergoes a physical change. Just that the molecules rearrange themselves a bit, without making any changes in the internal structure and composition.
So, when we switch on a bulb, electrons in the tungsten wire get excited and release energy in terms of photons. In all, there is just a temporary rise in temperature and release energy in the form of light. When we switch the bulb off, these things go back to normal in some period of time.
Hence, glowing of a bulb is a physical type of change.
So, option A is correct.

Additional information:
A substance is said to undergo a physical change when only the physical properties such as the shape, size, colour, state or appearance of the substance change.
 Its chemical composition remains intact. Some of the characteristics of a physical change are:
- Physical changes are temporary in nature.
- There is no formation of any new substance.
- Only the molecules get rearranged, but then the internal structure is intact.
- Most of the changes are reversible.

Note: Heating of the wire may cause it to expand and become red in colour. But these changes go back to normal when we switch the bulb off. Since, there is no permanent change, glowing of a bulb cannot be a chemical change.