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Lesson 5: Gas Pressure (Introductory) Particles in gases Collisions with container walls Pressure changes (qualitative only)
Year 8 • Chemistry
Lesson 5: Gas Pressure
In this lesson, students learn what gas pressure is and how it is caused by particles colliding with the walls of a container. Changes in pressure are explained qualitatively using the particle model.
Lesson Objectives
- Understand what gas pressure is.
- Describe how gas particles move.
- Explain pressure using particle collisions.
- Understand how pressure changes qualitatively.
1. Particles in Gases
Gas particles are far apart and move freely in all directions at high speed.
[ Image Placeholder – Particles in a Gas ]
Key ideas:
• Gas particles move quickly
• There is lots of empty space between particles
• Particles move randomly in all directions
• Gas particles move quickly
• There is lots of empty space between particles
• Particles move randomly in all directions
Real-life example:
Air fills any container because gas particles spread out.
2. Collisions with Container Walls
Gas pressure is caused by particles colliding with the walls of their container.
[ Image Placeholder – Gas Particle Collisions ]
• Each collision pushes on the container wall
• More collisions → greater pressure
• Stronger collisions → greater pressure
• More collisions → greater pressure
• Stronger collisions → greater pressure
Real-life example:
Air inside a balloon pushes outward on the rubber.
3. Pressure Changes (Qualitative)
Gas pressure can change when temperature or volume changes.
[ Image Placeholder – Pressure Changes ]
Qualitative explanations:
• Heating gas → particles move faster → pressure increases
• Cooling gas → particles move slower → pressure decreases
• Squeezing gas → particles collide more often → pressure increases
• Heating gas → particles move faster → pressure increases
• Cooling gas → particles move slower → pressure decreases
• Squeezing gas → particles collide more often → pressure increases
Real-life examples:
• A warm balloon expands
• Bicycle tyres feel harder on hot days
Practice Questions
A. Fill in the Blanks
- Gas particles are very far __________.
- Gas pressure is caused by particle __________.
- More collisions cause __________ pressure.
- Heating gas makes particles move __________.
- Squeezing gas increases __________.
B. True or False
- Gas particles move slowly.
- Gas pressure acts on container walls.
- Cooling gas increases pressure.
- Heating gas increases pressure.
- Gas particles move randomly.
C. Short Answer
- What causes gas pressure?
- Why does a balloon expand when heated?
- Why does squeezing gas increase pressure?
- How do gas particles move?
- Give one real-life example of gas pressure.
✅ Show Answer Key
A. Fill in the Blanks
- apart
- collisions
- higher
- faster
- pressure
B. True or False
- False
- True
- False
- True
- True
C. Short Answer
- Collisions of gas particles with container walls.
- Particles move faster and collide more.
- Particles collide more often.
- Quickly and randomly.
- Balloon / tyre / aerosol (any).
© Aviate Learning – Gas Pressure (Year 8)
💨 Interactive Gas Pressure Simulator
Change the temperature and container size to see how gas pressure changes.
Pressure depends on how often and how strongly particles collide with the container walls.
Higher temperature → particles move faster → more collisions → higher pressure.