Destructive distillation is a process in which a substance is heated to a high temperature in the absence of air (or with limited oxygen), causing it to decompose into simpler substances. This method is used to break down complex organic compounds into simpler compounds, which are then collected and condensed. For example, coal is destructively distilled to produce coke, coal tar, and gas. The process is “destructive” because it involves breaking down large molecules, and the products are often gases or liquids that are chemically different from the starting material.