Curious Kids: what is fire?

This is an article from Curious Kids, a series for children of all ages.

What is fire? — Lyra, age seven, Oxford, UK

Thanks for the question, Lyra. Basically, fire is light and heat that comes from a special kind of chemical reaction, which humans figured out how to make hundreds of thousands of years ago.

To understand how that reaction works, there are a few things that we need to learn about the world around us. Everything that you see and touch is made up of tiny things called atoms. You can think of atoms as really, really small bits of Lego — so small you can’t even see them.

Atoms join together to form molecules, and molecules join together to form the objects we can see and feel in everyday life. For example, wood is mainly made of a type of molecule called cellulose and each molecule of cellulose is made of atoms called carbon, oxygen and hydrogen.

Now, to see how the chemical reaction works, let’s imagine that you’re living in a cave 400,000 years ago, and that you’re one of the very first people to use fire.

You’re hungry and you want to cook an animal that you caught earlier in the day. On your way back to the cave, you collected some twigs and sticks for your fire. But there’s two other things you need before you can light the fire. You need oxygen — but…