What is a chemical, and what kinds are there?
In science, a chemical is any substance with a definite makeup. There are three main kinds you might hear about: elements, compounds, and mixtures. Here’s how to tell them apart in a simple way.
- Elements — one kind of atom. Examples: oxygen (O), hydrogen (H). Oxygen gas is made of O atoms joined together as O2, but it’s still the element oxygen.
- Compounds — two or more elements bonded together in a fixed recipe. Examples: water (H2O), table salt (NaCl), carbon dioxide (CO2).
- Mixtures — two or more substances that are together but not bonded in a fixed recipe. You can usually separate them by physical methods. Examples: trail mix, salt and pepper, air (a mix of gases).
How to tell which kind you have
- Look at the name or formula. If it has more than one element in a fixed ratio, it is a compound.
- If it is made of different things that you can separate physically, it is a mixture.
- If it has only one kind of element or a molecule made from one element (like O2), it is an element.
Quick, kid-friendly examples:
- O2 is an element (oxygen gas).
- H2O is a compound (water).
- NaCl is a compound (table salt).
- Air is a mixture (mostly nitrogen and oxygen).
Try a tiny activity with an adult
- Compare plain water and saltwater. They look similar but have different substances dissolved in them. That helps show the difference between compounds and mixtures.
If you tell me the name or formula of the chemical you’re curious about, I can tell you exactly what kind it is and why.