| State | Arrangement | Movement |
|---|---|---|
| Solid | Close together in fixed positions | Vibrate about fixed positions |
| Liquid | Close together, irregular arrangement | Move past each other |
| Gas | Far apart, random arrangement | Move rapidly in random directions |
Solids have a fixed shape and volume. Liquids keep their volume but take the container’s shape. Gases spread to fill the container and are easily compressed because there is lots of space between their particles. The particles themselves do not expand during a state change.
Melting: solid → liquid. Freezing: liquid → solid. Boiling: liquid → gas throughout the liquid at its boiling point. Condensing: gas → liquid. Evaporation can happen at the surface below the boiling point.
Below the melting point: solid. Between melting and boiling points: liquid. Above the boiling point: gas. At a melting or boiling point, two states can coexist during the change. Compare temperatures at the same pressure.
| Example substance | Melting point | Boiling point | At 20°C |
|---|---|---|---|
| A | −10°C | 80°C | Liquid |
| B | 50°C | 140°C | Solid |
| C | −90°C | −30°C | Gas |
| Symbol | Meaning |
|---|---|
| (s) | Solid |
| (l) | Liquid |
| (g) | Gas |
| (aq) | Aqueous: dissolved in water |
Example: H₂O(l) → H₂O(g). “Aqueous” does not mean pure liquid. NaCl(l) is molten salt; NaCl(aq) is salt dissolved in water.
Solid: vibrate. Liquid: move past. Gas: far apart and random. (aq) means dissolved in water.
Build confidence with pictures, clues and instant feedback.
One point for each answer you get right first time.
No timer. Take your time and use a clue whenever you need one.