Combustion

A candle on a birthday cake, a campfire in summer, the flame on a gas stove: fire is everywhere in your life. Behind it is always the same chemical reaction. Once you understand it, you also know how to put a fire out safely.

What is combustion?

Combustion is a chemical reaction with oxygen. A fuel like wood, wax, or gas reacts with the oxygen in the air, releasing energy as heat and light. Carbon, for example, reacts with oxygen to form carbon dioxide: C + O₂ gives CO₂. Just like when balancing equations, no atoms are lost here, they are only rearranged. One thing is important here: enough oxygen. If the flame gets too little of it, the carbon burns incompletely and the odourless, poisonous carbon monoxide CO is formed.

The fire triangle

A fire needs these three things at the same time: fuel, oxygen, and heat. If one of the three sides is missing, nothing burns. Extinguishing therefore means removing one side. Water cools the flames and takes away the heat. A fire blanket cuts off the oxygen and smothers the fire. And removing the fuel, for example by turning off the gas, also puts the fire out.

Why never use water on fat?

You must never use water to put out burning fat in a pan. The burning fat is hotter than 300 °C, the water sinks into it and vaporises instantly: a single spoonful of water becomes more than a thousand times as much steam, which hurls burning droplets of fat across the whole kitchen. The right way: turn off the stove and put on a fitting lid so no more oxygen reaches the flames. And most importantly: never experiment with fire on your own, only with adults or in class.