Kinetic Particle Model of MatterCopy
Cheat Sheet: States of Matter & Particle Model (O Level / IGCSE Physics)
2.1.1 States of Matter
1. Distinguishing Properties
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Shape | Fixed | Takes shape of container | No fixed shape |
| Volume | Fixed | Fixed | Fills entire container |
| Compressibility | Not easily compressible | Slightly compressible | Easily compressible |
| Particle motion | Vibrate in fixed positions | Slide past each other | Move freely and rapidly |
2. Changes of State
- Melting: Solid → Liquid
- Freezing: Liquid → Solid
- Boiling/Evaporation: Liquid → Gas
- Condensation: Gas → Liquid
(Sublimation and deposition not required)
2.1.2 Particle Model
1. Particle Structure of States
| State | Particle Arrangement | Forces | Motion |
|---|---|---|---|
| Solid | Tightly packed, fixed | Very strong | Vibrate about fixed positions |
| Liquid | Closely packed, no fixed positions | Medium | Move/slide over each other |
| Gas | Far apart, random | Negligible/weak | Move fast in all directions |
- Solids: strong intermolecular forces
- Liquids: weaker than solids, allow flow
- Gases: almost no intermolecular forces
2. Temperature and Particle Motion
- As temperature increases, particle speed increases
- Higher temp = higher kinetic energy
- At absolute zero (−273°C or 0 K):
- Particle motion theoretically stops
- No kinetic energy
- Known as the lowest possible temperature
3. Gas Pressure and Collisions
- Gas particles move randomly and collide with container walls
- Each collision exerts a force on the wall
- Pressure = total force per unit area due to collisions
- More frequent or forceful collisions = higher pressure
4. Particle Explanations of Gas Laws
(a) Pressure ∝ Temperature (at constant volume)
- As temperature increases, particles move faster
- More frequent and forceful collisions with container walls
- → Pressure increases
(b) Volume ∝ Temperature (at constant pressure)
- To keep pressure constant:
- When temperature increases, gas expands
- Particles move faster and need more space to maintain same pressure
(c) Pressure ∝ 1/Volume (at constant temperature)
- If volume decreases, particles collide more often
- → Pressure increases (inverse relationship)
5. Gas Pressure-Volume Relationship (Boyle’s Law)
- Equation:
p₁ × V₁ = p₂ × V₂
(at constant temperature) - Graph:
- Pressure vs Volume: Curved (inversely proportional)
- Pressure vs 1/Volume: Straight line
- Units must be consistent (Pa & m³ or kPa & cm³)
- Assumes fixed mass of gas and constant temperature