At boiling point of liquids, its A. Temperature increases B. Atmospheric pressure increases C. Temperature remains constant D. Vapour pressure decreases

The correct answer is C. Temperature remains constant.

Boiling point is the temperature at which the vapor pressure of a liquid equals the external pressure surrounding the liquid and the liquid changes into a vapor. At the boiling point, the liquid is in equilibrium with its vapor phase. The temperature of a boiling liquid does not change until all of the liquid has been converted into vapor.

A. Temperature increases is incorrect because the temperature remains constant at the boiling point.

B. Atmospheric pressure increases is incorrect because the atmospheric pressure does not affect the boiling point of a liquid. The boiling point of a liquid is only affected by the vapor pressure of the liquid.

D. Vapour pressure decreases is incorrect because the vapor pressure of a liquid increases at the boiling point.