Question

Assertion (A): When hot water is poured in a thick glass tumbler then the tumbler breaks.
Reason (R): Glass is a bad conductor of heat

• A. A and R are correct and R is correct
  explanation for A
• B. A and R are correct and R is not correct
  explanation for A
• C. A is true and R is false
• D. A is wrong and R is true.

Answer 1

The correct option is A A and R are correct and R is correct

explanation for A
When hot water is poured into a thick tumbler its inner surface expands. However, Since glass is bad conductor of heat , the heat does not go to outer surface and the expansion of outer surface of the tumbler is quite small. Due to uneven expansion of the outer and inner surfaces, the tumbler breaks. because the heat will try to escape but the glass would not allow it and in the process ultimately glass breaks down.