1. Meaning of Matter
Matter is anything that has mass and occupies space.
Examples: Air, water, wood, stones and metals.
2. States of Matter
Solid
- Definite shape and volume.
- Particles are closely packed.
- Particles vibrate about fixed positions.
- Difficult to compress.
Liquid
- Definite volume but no definite shape.
- Takes the shape of its container.
- Particles can slide past one another.
- Slightly compressible.
Gas
- No definite shape or volume.
- Particles are far apart.
- Particles move randomly and rapidly.
- Easily compressed.
3. Kinetic Theory of Matter
The kinetic theory states that:
- Matter is made up of tiny particles.
- Particles are in constant motion.
- There are forces of attraction between particles.
- Increasing temperature increases the average kinetic energy of particles.
4. Diffusion
Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration.
Examples:
- Perfume spreading through a room.
- Smell of cooking spreading through a house.
Factors affecting diffusion:
- Temperature.
- Concentration difference.
- Particle size.
- Nature of the medium.
5. Brownian Motion
Brownian motion is the continuous random movement of tiny particles suspended in a liquid or gas.
Cause: Unequal collisions by the rapidly moving molecules of the surrounding fluid.
Importance: Provides evidence that molecules are in constant random motion.
6. Changes of State
| PROCESS | CHANGE |
| Melting | Solid → Liquid |
| Freezing | Liquid → Solid |
| Evaporation | Liquid → Gas |
| Boiling | Liquid → Gas |
| Condensation | Gas → Liquid |
| Sublimation | Solid → Gas |
7. Evaporation and Boiling
| EVAPORATION | BOILING |
| Occurs at the surface | Occurs throughout the liquid |
| Occurs at any temperature | Occurs at a fixed boiling point for a given pressure |
| Slow process | Rapid process |
| Causes cooling | Requires heat energy |
8. Density
Density is the mass per unit volume of a substance.
Formula:
Density = Mass / Volume
Common units:
- kg/m³
- g/cm³
Remember:
- High density means more mass per unit volume.
- Low density means less mass per unit volume.
9. Latent Heat
Latent heat is the heat energy absorbed or released during a change of state without a change in temperature.
Two types:
1. Specific latent heat of fusion: Heat required to change 1 kg of a solid into liquid at constant temperature.
2. Specific latent heat of vaporisation: Heat required to change 1 kg of liquid into gas at constant temperature.
10. Important Facts to Remember
- Solids have the strongest intermolecular attraction in the basic particle model.
- Gas particles have the highest freedom of movement.
- Heating increases the average kinetic energy of particles.
- Cooling decreases the average kinetic energy of particles.
- Gases are more compressible than liquids and solids.
- Diffusion occurs faster in gases than in liquids under ordinary comparable conditions.
- Brownian motion provides evidence for the kinetic theory of matter.
- During a change of state, temperature remains constant for a pure substance at constant pressure while the phase change is occurring.
Essential WASSCE Formula
| QUANTITY | FORMULA |
| Density | Mass / Volume |
| Mass | Density × Volume |
| Volume | Mass / Density |
| Specific latent heat | Heat energy / Mass |
Quick WASSCE Revision: Important Points
| CONCEPT | KEY FACT |
| Matter | Has mass and occupies space |
| Solid | Definite shape and volume |
| Liquid | Definite volume, no definite shape |
| Gas | No definite shape or volume |
| Diffusion | Movement from higher to lower concentration |
| Brownian motion | Random movement of suspended particles |
| Density | Mass per unit volume |
| Sublimation | Solid directly to gas |
| Evaporation | Occurs at the liquid surface |
| Condensation | Gas changes into liquid |
| Melting | Solid changes into liquid |
| Freezing | Liquid changes into solid |
WASSCE examination tip: Master the three states of matter, kinetic theory, diffusion, Brownian motion, density and changes of state. These are important foundations for WASSCE Physics questions.
Pay particular attention to the differences between diffusion and Brownian motion, evaporation and boiling, and density and relative density. These are common areas for testing conceptual understanding.
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