Question

Why does the glass break on sudden heating?
A. all parts of glass expands equally
B. all parts of glass don’t expand equally
C. high temperature makes the substance unstable
D. glasses are easy to break

Answer 1

Hint: Thermal shock is the phenomenon where the different parts of an object expand to different amounts due to change in temperature. This is caused due to the stress or strain occurring. Extreme heat can expand the glass in a nonuniform manner which will cause the breaking.

Complete answer:
When we pour the hot water on a glass, suddenly, it breaks. This is because when we pour hot water suddenly, we instantly heat the glass plate, only the inner layer of the glass will be absorbing heat. When a substance absorbs heat, it gets expanded. Glass is no exception in this case. As we all know glass is not a good conductor, the conduction of heat through the glass layer will be weaker. Therefore, the inner layer of the glass will be hot but the outer layer will be still relatively cold. This difference in temperature is the reason for the inner layer of the glass in order to expand up to a limit more than the outer layer. The variation in the measure of expansion will provide a huge amount of pressure on the outer layer of the glass. If the glass is unable to withstand this high pressure, it will begin to crack. The magnitude of the temperature variation between the inner and outer layers will cause the chance for the cracking of glass. If the required heat is provided, the glass will surely crack.

So, the correct answer is “Option B”.

Note:
it is to be noted that how thinner the glass will be, the lesser the chance to get cracked. The chance of cracking the glass is dependable on the difference between the temperature of inner and outer layers of the glass. Therefore there are chances for cracking a hot glass with cold water.