Internal combustion engines are everywhere, yet they are not a common sight. They power most cars and motorcycles by combusting a fossil fuel like petroleum (although these vehicles are slowly being replaced by electric vehicles).
Combustion is a type of chemical reaction called a redox reaction, short for ‘reduction-oxidation’. Here, one substance loses electrons and the other gains them. The losing substance is called the oxidant. (Historically, the oxidant was a substance that provided oxygen atoms in a reaction. Over time chemists generalised the term to include all substances that participated in a chemical reaction the way oxygen did, by donating electrons.) The gaining substance is called the reductant. During combustion, the fuel is the reductant.
All combustion reactions release energy. Sometimes, the heat energy in this release will vaporise the fuel, producing a flame. The combustion reaction also releases a gaseous mix of highly oxidised matter called smoke. Combustion science is the branch of science devoted to studying combustion. The combustion of fossil fuels in internal combustion engines and industrial processes is an important cause of global warming.
Combustion scientists study the reaction in different ways — including in space — to understand the different ways it can be controlled and the reaction products made cleaner.
