C1G

alcohol + acid → ester + water

A perfume must evaporate so that the perfume molecules can reach the nose easily.

Perfumes are insoluble in water so that the perfume does not wash off easily.

Esters are chemicals with pleasant smells. They are used in perfumes, and as solvents.

Volatile liquids evaporate easily. They readily change from a liquid to a gas. This is because there are only weak attractive forces between particles in the substance. These forces are overcome easily, so particles with enough energy can escape from the liquid.

The EU has banned all testing of cosmetics on animals because public opinion is strongly against it. 

Because nail varnish is insoluble in water.