Elements, Compounds & Mixtures
Year 7 ⚛️ Particles & Structure Distinguish between elements, compounds and mixtures with examples.
⚛️ Elements
An element is a pure substance made of only one type of atom. Elements cannot be broken down into simpler substances by chemical means.
Examples: Iron (Fe), Copper (Cu), Oxygen (O₂), Carbon (C), Gold (Au), Sulfur (S).
There are 118 known elements, all listed in the Periodic Table.
🔗 Compounds
A compound contains two or more elements chemically combined in a fixed ratio. Compounds have different properties from their constituent elements.
| Compound | Elements combined | Formula |
|---|---|---|
| Water | Hydrogen + Oxygen | H₂O |
| Salt | Sodium + Chlorine | NaCl |
| Carbon dioxide | Carbon + Oxygen | CO₂ |
| Ammonia | Nitrogen + Hydrogen | NH₃ |
🌀 Mixtures
A mixture contains two or more substances not chemically combined. The substances keep their own properties and can be separated by physical means.
Examples: Air (N₂ + O₂ + Ar + CO₂), sea water (water + salt), sand and iron filings, crude oil.
Key Differences
$$\text{Element: one type of atom} \quad \text{Compound: fixed ratio, chemically bonded}$$
$$\text{Mixture: variable ratio, physically mixed, separable}$$
Ready to test yourself? Click the Quiz tab above to practise questions on this topic!
Interactive Demonstration — Elements, Compounds & Mixtures
Drag each substance into the correct category.
⚛️ Elements
🔗 Compounds
🌀 Mixtures
Iron (Fe)
Water (H₂O)
Air
Oxygen (O₂)
Salt (NaCl)
Seawater
Gold (Au)
CO₂
Click each substance to classify it.
⚗️ Element / Compound / Mixture Classifier
Calculate the purity of a substance from a sample containing impurities.