Final answer:
The method using steam or boiling water to extract essences of plants is known as distillation. This process leverages differences in volatility to separate substances and is widely used both in the laboratory and industrial settings.
Step-by-step explanation:
A method of using steam or boiling water to extract essences of plants is called distillation. This technique involves heating a liquid to create vapor which is then condensed back into liquid and collected. The process separates substances based on differences in volatility or boiling points. For plant essences, the steam distillation method allows the extraction of volatile components, often termed essential oils, from the plant material.
Distillation is not only used for plant essences but also widely applied in both laboratory and industrial settings, where it can be used to refine petroleum, isolate fermentation products, and purify water. In the laboratory, Raoult's law shows that a vapor above a solution is enriched in the more volatile component, allowing for efficient separation when the mixture is heated.