Hello, the word molecule turns up all the time in science, but it can actually be a really difficult word to use correctly. Well, if you stick with me for the next three minutes, you'll know what this word means and be able to use it correctly whenever you need to in the future. Google will tell us that a molecule is a group of atoms bonded together, bloody, bloody blah, the key bit is there at the beginning. A molecule is a group of atoms bonded together, and we're normally talking about a small group of molecules of atoms. Take water, for example, H2O, it looks something like this. We have an oxygen atom that forms two covalent bonds to hide shenanigans, and that's it, that's the molecule. There's nothing more to it than that. Now, if I fill a glass with water, all I'm doing is adding lots and lots of molecules until the glass is full. Each molecule is three atoms, and it's held together by strong covalent bonds, but between the molecules, there are no very strong forces acting at all. As you can see, these molecules are really small, but molecules appear in all living things and throughout the world, and they can be much bigger. They can be things like sugars or proteins or DNA or other polymers, but for the most part, the molecules that you will need to know about, if you're doing GCSEs or exams like that, are small molecules that just contain a few atoms. Here's a key thing to know about molecules. Molecules pretty much never contain metal atoms. So, if you read about a chemical like sodium chloride or magnesium sulfate or copper, you can know that they are not molecules because they contain some metal within them. Molecules are made up of non-metal atoms that are covalent bonded together, and normally we're talking about a small number of them stuck together. I've used the picture of Cheerios because they're a little bit like Cheerios. If you think each Cheerio is a molecule, it's held together by some strong stuff holding it together, but then between the Cheerios, there aren't very many strong forces. Well, that's a bit like what molecules are. A small number of atoms strongly held together, but then between those molecules, there aren't very many strong forces at all. Hopefully that explains to you what a molecule is, and you'll never feel like you don't know when to use the word again. That's it from me for now. Don't stop believing.