If a liquid is heated and the temperature at which it boils is measured, the property is being measured. a molecular b physical c atomic d chemical

B physical

Explanation:

The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to the vapor pressure of the surrounding gas. It is the temperature at which a liquid turns to vapor.

The physical property of a substance is devoid of a change in the chemical composition of that substance. Physical change is only accompanied by change in the physical state but their is no overall change in the chemical composition.  Example of physical properties are freezing point, boiling points, hardness, color and electrical conductivity.

Chemical change is accompanied with change in the chemical composition of that substance. Usually , a new substance is formed . Example of chemical properties are rusting and combustion.

The heating of a liquid to ascertain the boiling points is a measure of the physical property . The liquid didn't change in it chemical composition . It only change it physical state and no new substance is formed . That is it possess the same chemical composition.    

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.