Why is water favored for use in steam distillation?

Water is favored for use in steam distillation primarily due to its low molecular weight and its unique properties that facilitate the separation of organic compounds. The low molecular weight of water enables it to vaporize readily, even at temperatures that are lower than the boiling points of many organic compounds. This characteristic allows steam distillation to be performed effectively without subjecting sensitive organic materials to high temperatures that could lead to their degradation or decomposition.

Additionally, the low boiling point of steam (100°C) allows for the extraction of thermally sensitive compounds while minimizing the risk of thermal degradation. During steam distillation, the presence of water in vapor form effectively increases the total vapor pressure, allowing for the co-distillation of both water and the organic compound of interest. This process enhances the separation and purification of the organic compounds without requiring them to reach their boiling points directly.

While some of the other options present valid properties of water, they do not encapsulate the primary reason for its preference in steam distillation as effectively as the low molecular weight does.