What is the process called when a material decomposes upon being exposed to heat in the absence of oxygen?

The process of decomposition of a material when exposed to heat in the absence of oxygen is known as pyrolysis. This thermal degradation process breaks down complex organic molecules into simpler compounds, typically resulting in a mix of gases, liquids, and solid residues, like charcoal. Pyrolysis takes place in a controlled environment where there is no oxygen, preventing combustion, which would require oxygen to occur.

While combustion involves the rapid reaction between a material and oxygen, leading to fire and heat, pyrolysis occurs more gradually and at lower temperatures, without producing flames. This characteristic distinguishes pyrolysis from the other processes listed. Oxidation refers to a reaction where a substance loses electrons, often in the presence of oxygen, and recombination describes the process of combining elements or compounds to form new ones, neither of which accurately describes the heat-driven decomposition of materials in the absence of oxygen.