✅ What is Diffusion? (KS3)

Diffusion is the movement of particles from an area of high concentration to an area of low concentration (where there are fewer of them).
It happens because particles are always moving and “spread out” until they are evenly distributed.

📘 Diffusion in Living Organisms:

• Cells need substances like glucose (sugar) and oxygen to survive.
• They also need to remove waste products like carbon dioxide.
• These materials move into or out of cells by diffusion.
• Example: Glucose moves from outside the cell (lots of glucose) into the cell (not much glucose) through the cell membrane.

📗 Diffusion in the Air:

• Diffusion is just particles spreading out.
• Example: A smell in a room — smell particles spread from high concentration (near the source) to low concentration (the rest of the room).
• Diffusion is slow, because particles bump into air particles and change direction often.

🔑 Simple Definition for Students:

Diffusion is the movement of particles from where there are lots of them to where there are fewer of them, until they are spread out evenly.