Distillation is an effective way to purify liquids or to separate the components of a liquid mixture. An example of purification is distilling potable water from sea water. When sea water is heated to boiling, water molecules rapidly enter the vapor phase while salt (and other non-volatile contaminants) remain in the heated container. This vapor then condenses into drinking water that is much more pure than the original sea water. An example of component separation is the process of refining crude oil, which is a mixture of many distinct hydrocarbon compounds. These compounds have different uses -- for example, some are valuable for fuels such as gasoline while others are better for lubricating oil. These compounds have different boiling points, so oil refineries can employ a specialized distillation procedure to isolate them.