Final answer:
Steam distillation is used for separating compounds in a mixture through co-distillation with steam, often applied for volatile, heat-sensitive substances. It uses homogeneous mixtures, and unlike vacuum distillation - which operates below atmospheric pressure enabling lower boiling points - steam distillation relies on water vapor and operates at temperatures that prevent decomposition of delicate materials.
Step-by-step explanation:
Steam distillation is a technique commonly used for purifying and separating compounds of a mixture that are temperature-sensitive. It is particularly useful for isolating volatile organic compounds from non-volatile or less volatile ones. The method involves co-distilling a compound with water (steam). The mixtures used in steam distillation are usually homogeneous mixtures of compounds with significantly different vapor pressures. This method is applied to separate essential oils from plants, flavorings, and fragrances.
The difference between vacuum distillation and steam distillation lies in the operating pressure and the presence of steam. In vacuum distillation, the pressure above the liquid mixture is reduced to below atmospheric pressure, meaning that mixtures can be distilled at temperatures lower than their normal boiling points. Conversely, steam distillation employs water vapor along with the compound, enabling the separation of heat-sensitive substances at temperatures lower than their decomposition temperatures, making it ideal for delicate materials.
For example, vacuum distillation is widely used in refining petroleum to isolate different fractions like gasoline and diesel. Steam distillation, on the other hand, is utilized to extract essential oils, where direct heating could lead to the degradation of desired compounds.