Final answer:
Steam distillation is used to separate an oil from plants by heating a mixture of water and plant material, allowing the plant oils to vaporize with the steam and then condensing them separately based on their different boiling points.
Step-by-step explanation:
Steam distillation can be used to separate an oil from plants by exploiting the different boiling points of water and the plant oils. Typically, the plant material is placed in a distillation apparatus along with water. As the mixture is heated, steam passes through the plant material, vaporizing the volatile compounds (oil) along with the steam. Due to their differences in boiling points, the vaporized oil and water can be efficiently separated. The vapors are cooled in a condenser, resulting in a mixture of oil and water, which usually separate into layers due to their distinct densities, allowing for easy separation.
Referring to large-scale processes, like those used in oil refineries, the distilled components from crude oil are collected in a fractionating column as they reach different heights corresponding to their condensation temperatures. The principle is the same for plant oils; however, with steam distillation, the plant oils are being separated from the water. Different components, based on boiling temperature, will condense at different points in the column, making it possible to isolate and collect the desired oil.
Furthermore, just as oil refineries use this process to obtain products such as gasoline, kerosene, and diesel fuel, steam distillation is applied to obtain essential oils from plant material, each with their unique boiling points that allow for separation from the steam and other plant components.