Science
How does osmosis work?
Osmosis works when water moves across a semi-permeable membrane from where it's more dilute to where it's more concentrated, trying to balance the two sides. The membrane lets water through but blocks the dissolved particles, so water flows until both sides are evenly mixed — how plant roots drink and how your cells stay balanced.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how osmosis works.
Step by step
- 1Water crosses a semi-permeable membrane.
- 2It flows toward the more concentrated side.
- 3The membrane blocks dissolved particles.
- 4It balances concentration on both sides.
Frequently asked questions
- How does osmosis work?
- Water passes through a membrane from the dilute side to the concentrated side until both are balanced, while dissolved solids stay put.
- Why is osmosis important for living things?
- It's how plant roots absorb water and how cells keep the right water balance to survive.
- What's the difference between osmosis and diffusion?
- Diffusion is any particles spreading out; osmosis is specifically water moving across a membrane.