Saturated vs Unsaturated
Saturated
Saturated has two chemical meanings sharing the idea of a full capacity. (1) A saturated solution contains the maximum amount of dissolved solute possible at a given temperature — no more will dissolve. (2) A saturated hydrocarbon contains only single bonds between carbon atoms, so each carbon carries the maximum number of hydrogen atoms.
Example: A salt solution with 36 g of dissolved NaCl per 100 g of water at 20 °C is saturated; so is ethane (C2H6), whose carbons share only single bonds.
Unsaturated
Unsaturated also has two meanings. (1) An unsaturated solution can still dissolve more solute at the given temperature — it is below capacity. (2) An unsaturated hydrocarbon contains at least one carbon–carbon double or triple bond, so the carbons carry fewer hydrogen atoms than the maximum.
Example: Ethene (C2H4), with one C=C double bond, is unsaturated — and it reacts with bromine, which ethane will not do.
Key differences
| Aspect | Saturated | Unsaturated |
|---|---|---|
| Meaning in solutions | A solution that has dissolved the maximum amount of solute possible at a given temperature. | A hydrocarbon that contains the maximum number of hydrogen atoms per carbon. |
| Unsaturated counterpart | Can dissolve more solute; more can still be added. | Contains at least one double or triple bond between carbons, so fewer hydrogens fit. |
| How you tell which it is | Adding more solute causes undissolved crystals to sit at the bottom of the container. | Testing with bromine water: unsaturated compounds decolorize it, saturated ones do not. |
| Concrete example | Salt water at 20 °C holding 36 g of NaCl per 100 g of water. | Methane (CH4) and ethane (C2H6), with all single bonds between carbons. |
| Fat example | Olive oil's oleic acid, with one C=C double bond, is an unsaturated fat. | Butter's stearic acid, with only single bonds, is a saturated fat — solid at room temperature. |
'Saturated' is used in two different branches of chemistry, so context decides the meaning: in solutions it means 'holding as much dissolved solute as possible,' while in organic chemistry it means 'holding as many hydrogen atoms as possible.' The two ideas are related by the image of a capacity being full, but the capacity is different. Also, a saturated fat can be dissolved in an unsaturated solution — the words can legitimately appear in the same sentence with different meanings.