Question

You are given two samples of water labelled as “A “ and ”B”. Sample “A” boils at ${100}^{\circ }\mathrm{C}$ and sample B bBoils at ${102}^{\circ }\mathrm{C}$. Which sample of water will not freeze at $0^{\circ }\mathrm{C}$. Comment.

Answer 1

Sample A:

• The boiling point of pure water is ${100}^{\circ }\mathrm{C}$ at $1\mathrm{atm}$ pressure, and the melting point is $0^{\circ }\mathrm{C}$ at $1\mathrm{atm}$ pressure.
• The only pure substance has such a sharp melting point.

Sample B:

• When water contains some impurities, the boiling point rises and the melting point falls.
• Because sample 'B' is not pure water, as it has boiling point ${102}^{\circ }\mathrm{C}$ which is greater than ${100}^{\circ }\mathrm{C}$, and its melting point is lower than $0^{\circ }\mathrm{C}$ so it will not freeze at $0^{\circ }\mathrm{C}$.