This document defines and describes several scientific terms: air is a mixture of nitrogen, oxygen, and other gases; alloy is a mixture of metals; boiling point refers to the temperature at which a liquid turns to a gas, such as water boiling at 100 degrees Celsius. Chromatography is described as a method to separate substances as they move through a material like paper at different speeds. A condenser is a device that cools a gas into a liquid, and crude oil is defined as a valuable mixture of hydrocarbons that can be extracted to produce useful chemicals.