This was a great question that really got me thinking about how to explain molecular chemistry to a 5-year-old.
The chemical formula for water is familiar to many of us. It’s something we learn early on in science at school. But what is water and how is it made?
Water is made up of two chemical elements: hydrogen and oxygen. You can find them in the periodic table by their symbols: H and O. Water has the chemical formula H2O, which means that each water molecule is made up of two hydrogen atoms joined to one oxygen atom.
Hydrogen and oxygen both occur naturally as gases. They can also exist as liquids but only when they get really, really, really cold.
Hydrogen is one of the gases that our Sun is made of. It is very important in chemistry and biology because it can join up with lots of other chemical elements to make different molecules. Hydrogen is the smallest and lightest element. It is much lighter than air – if you fill a balloon with hydrogen, it will float upwards.
Oxygen is one of the gases in air. It is the gas that our lungs take from the air when we breathe. Oxygen is also very important for chemistry and biology as it too combines with lots of other chemical elements to make different molecules.
To find out more about hydrogen and oxygen, take a look at this interactive periodic table.
But, if you take hydrogen and oxygen and mix them together, you don’t get water – you just get an invisible mixture of two gases! So, how do you turn the atoms of these two gases into the molecules of liquid water? You need something that will cause a chemical change – heat.
If you take a mixture of hydrogen and oxygen gases and set them on fire (please don’t try this at home!!!), you will hear a squeaky-pop-bang as the hydrogen and oxygen atoms combine together to make water.
Here’s a video of someone doing just that: Listen out for the noise!