Lesson 6 of 7
Diffusion
Goal: Explain diffusion using the particle model.
The particles in liquids and gases move about at random. Bit by bit they spread out and mix. This is diffusion.
- From high concentration to low concentration. Particles spread from where there are many to where there are few, until they are evenly mixed.
- Diffusion is faster in a gas than in a liquid. Gas particles are far apart, so each one travels a long way before it hits another. In a liquid the particles are packed together, so they keep bumping into each other.
- Heating speeds it up, because hotter particles move faster.
How do we know particles move?
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Key words in this lesson
Particle A tiny piece of matter, far too small to see
Particle model The idea that everything is made of tiny moving particles
Liquid Flows and takes the shape of its container, but has a fixed volume
Gas Spreads out to fill its container, and can be squashed
Diffusion Particles spreading out from where there are many to where there are few