🔹 1. The Three States of Matter
Matter exists in three physical states:
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Shape | Fixed | Takes shape of container | No fixed shape |
| Volume | Fixed | Fixed | Not fixed (compressible) |
| Particle arrangement | Tightly packed & regular | Close but irregular | Far apart and random |
| Particle movement | Vibrate in fixed position | Move slowly & slide past | Move rapidly in all directions |
| Energy level | Lowest | Medium | Highest |
🔹 2. Particle Theory of Matter
The particle theory explains the properties of solids, liquids, and gases by considering:
- All matter is made of tiny particles.
- These particles are in constant motion.
- The forces of attraction between particles vary depending on the state.
✅ Example:
- Ice (solid): Particles vibrate but stay in place.
- Water (liquid): Particles move more freely than in a solid.
- Steam (gas): Particles move rapidly and are far apart.
🔹 3. Changes of State
Substances can change from one state to another when heat is added or removed:
| Change | Process Name | Energy Involved |
|---|---|---|
| Solid → Liquid | Melting | Heat absorbed |
| Liquid → Solid | Freezing | Heat released |
| Liquid → Gas | Boiling/Evaporation | Heat absorbed |
| Gas → Liquid | Condensation | Heat released |
| Solid → Gas | Sublimation | Heat absorbed |
| Gas → Solid | Deposition | Heat released |
✅ Example:
- Melting: Ice → Water at 0°C
- Boiling: Water → Steam at 100°C
- Sublimation: Solid iodine or dry ice (solid CO₂) → Vapour
🔹 4. Heating Curve of a Substance
Draw the heating curve of water starting from ice.
🔹 5. Diffusion
Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration. It happens fastest in gases and slower in liquids.
✅ Examples:
- Bromine gas diffusing in air (reddish-brown gas spreads in a glass jar).
- Smell of perfume spreading in a room.
🧪 Experiment: Place ammonia and hydrogen chloride at opposite ends of a glass tube. A white ring of ammonium chloride forms closer to the HCl side (since ammonia molecules are lighter and faster).
🔹 6. Factors Affecting Diffusion
- Mass of particles: Lighter particles diffuse faster.
- Temperature: Higher temperature = faster diffusion.
- State of matter: Gases > liquids > solids in terms of diffusion speed.
🔹 7. Brownian Motion
Brownian motion is the random movement of small particles suspended in a fluid (liquid or gas), caused by collisions with faster-moving molecules.
✅ Example:
- Pollen grains dancing on water surface
- Smoke particles under a microscope
🔹 8. Kinetic Theory Summary
- All particles are in motion.
- Heating = more kinetic energy → particles move faster.
- Cooling = less kinetic energy → particles move slower.
⭐️ Summary Table
| State | Arrangement | Movement | Energy | Compressibility |
|---|---|---|---|---|
| Solid | Tightly packed | Vibrate in place | Low | No |
| Liquid | Close, irregular | Slide past each other | Medium | Slight |
| Gas | Far apart | Move freely | High | Yes |
📌 Common Exam Questions
- Draw and label diagrams to show particle arrangement in solid, liquid, and gas.
- Explain why gases diffuse faster than liquids.
- Describe what happens to the particles when a solid melts.
- Why does the white ring of ammonium chloride form closer to the HCl end?
>>> Go to the main course
Have Questions? Speak to an Expert: 01817 122800
