Question

Assertion: Glass panes fixed to windows or doors of old buildings are slightly thicker at the bottom than at the top.
Reason: Glass is pseudo solid or supercooled liquid.
A. Both assertion and reason are correct and Reason is the correct explanation of Assertion.
B. Both assertion and reason are correct but reason is not the correct explanation for assertion.
C. Assertion is correct but reason is incorrect.
D. Both assertion and reason are incorrect.

Answer 1

Hint: We know that glass is made up of sand. The molecules within the glass can move so it is not a perfect solid. There are two types of solid, one is crystalline solids and the other is amorphous solids. Crystalline solids have definite melting points but amorphous solids do not have definite melting points.

Complete answer:
We know that glass is an amorphous solid. It is not a crystalline solid. It is also known as supercooled liquid. It has very high viscosity. Because of this reason it can behave like a fluid. The characteristic so fluid is that the molecules can flow. So similarly, the molecules of the glass flow downward because of the gravity. Because of this flow the bottom of the glass panes becomes thicker as compared to the top. For this reason, glass is also known as pseudo solid.
From the above explanation it is clear to us that the glass panes fixed to windows or doors of old buildings are slightly thicker at the bottom than at the top because glass is pseudo solid or supercooled liquid.

Hence, the correct answer of the given question is option (A). Both assertion and reason are correct and Reason is the correct explanation of Assertion.

Note:
Always remember that glass is a pseudo solid or supercooled solid. The molecules of the glass can flow within it and because of it the glass is thicker at the bottom when kept for many years. Crystalline solids have well defined edges but amorphous solid like glass do not have well defined edges.