Sorting everyday things into piles
Water, air and pure gold are on one shelf. Which pile does each belong to?
Step 1 of 4
- Three piles: element, compound, mixture.
- Element: one kind of atom only.
- Compound: joined atoms, fixed ratio.
- Mixture: two or more kinds, loose, amounts vary.
Pure gold is an element. Water is a compound. Air is a mixture.
The rule
Count the substances first. Two or more means a mixture. One substance is an element or a compound. A compound can be split into simpler substances by a chemical change. An element cannot.
| Thing | Pile | Why |
|---|---|---|
| Pure gold | Element | One substance. Nothing simpler. |
| Water | Compound | Hydrogen and oxygen, 2 to 1 |
| Sodium chloride | Compound | Sodium and chlorine, 1 to 1 |
| Air | Mixture | Several gases, not joined |
| Sea water | Mixture | Water and salt, not joined |
| Brass | Mixture | Copper and zinc, not joined |
Sort eight things. Count the substances first.
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