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Lesson 4: Diffusion What is diffusion? Diffusion in gases and liquids Effect of temperature
Year 8 • Chemistry
Lesson 4: Diffusion
In this lesson, students learn about diffusion and how particles spread out. Diffusion in gases and liquids is explained using the particle model, along with the effect of temperature on the speed of diffusion.
Lesson Objectives
- Define diffusion.
- Describe diffusion in gases and liquids.
- Explain diffusion using particle movement.
- Understand how temperature affects diffusion.
1. What Is Diffusion?
Diffusion is the movement of particles from an area of high concentration to an area of low concentration.
[ Image Placeholder – Diffusion Diagram ]
Key points:
• Happens because particles are always moving
• Continues until particles are evenly spread
• Does not need stirring
• Happens because particles are always moving
• Continues until particles are evenly spread
• Does not need stirring
Real-life example:
The smell of perfume spreading across a room.
2. Diffusion in Gases
Diffusion happens fastest in gases because gas particles are far apart and move quickly.
[ Image Placeholder – Diffusion in Gases ]
• Gas particles move freely
• Large spaces between particles
• Diffusion is very fast
• Large spaces between particles
• Diffusion is very fast
Example:
Cooking smells spreading through a house.
3. Diffusion in Liquids
Diffusion also occurs in liquids but more slowly than in gases.
[ Image Placeholder – Diffusion in Liquids ]
• Liquid particles are closer together
• Particles can still move past each other
• Diffusion is slower than in gases
• Particles can still move past each other
• Diffusion is slower than in gases
Example:
Food colouring spreading slowly in water.
4. Effect of Temperature on Diffusion
Temperature affects how fast diffusion happens.
[ Image Placeholder – Temperature Effect on Diffusion ]
• Higher temperature → particles move faster
• Faster particles → faster diffusion
• Lower temperature → slower diffusion
• Faster particles → faster diffusion
• Lower temperature → slower diffusion
Real-life example:
Food colouring spreads faster in warm water than in cold water.
Practice Questions
A. Fill in the Blanks
- Diffusion is the movement of particles from __________ to __________ concentration.
- Diffusion happens because particles are always __________.
- Diffusion is fastest in __________.
- Increasing temperature makes particles move __________.
- Diffusion in liquids is __________ than in gases.
B. True or False
- Diffusion happens in solids.
- Gas particles move freely.
- Diffusion needs stirring.
- Higher temperature increases diffusion speed.
- Particles stop moving when diffusion finishes.
C. Short Answer
- What is diffusion?
- Why is diffusion faster in gases?
- Give one example of diffusion in liquids.
- How does temperature affect diffusion?
- Why does perfume spread through air?
✅ Show Answer Key
A. Fill in the Blanks
- high, low
- moving
- gases
- faster
- slower
B. True or False
- False
- True
- False
- True
- False
C. Short Answer
- Movement of particles from high to low concentration.
- Particles are far apart and move fast.
- Food colouring in water.
- Higher temperature makes diffusion faster.
- Gas particles move freely.
© Aviate Learning – Diffusion (Year 8)