Q1.
Solids have a definite volume; what about liquids and gases?
Answer
A liquid has a definite volume but no fixed shape. A gas has neither.
| State | Shape | Volume | The reason, in terms of particles |
|---|---|---|---|
| Solid | Definite | Definite | Particles closely packed and held in fixed positions by the strongest attractions; they can only vibrate |
| Liquid | Not fixed | Definite | Attraction a little weaker, so particles move — but only within a limited space, and they stay close together |
| Gas | Not fixed | Not fixed | Attraction negligible, so particles move freely in all directions and spread into all the space available |
The book proves both of these to you:
- Activity 7.4 — the same water poured through Containers A, B and C takes the shape of each one, yet the level stays at the 200 mL mark every time. No fixed shape, fixed volume.
- Activity 7.5 — smoke collected in Gas Jar A spreads on its own until it fills the whole of Gas Jar B as well. Neither shape nor volume is fixed.
Note about Table 7.1: ice melts at 0 °C, urea at 133 °C and iron at 1538 °C. The same three solids, the same three states — but the temperature at which each gives way tells you how strong its interparticle attractions are.