Water follows the crowd
Osmosis moves water to the more concentrated side.
Two bags of different strength
A thin membrane separates a weak sugar solution from a strong one. Sugar cannot pass through it, but water can.
Which way will the water mostly move?
What this lesson covers
The idea
Osmosis is the diffusion of water across a selectively permeable membrane, from a dilute solution (more water, less solute) to a concentrated solution (less water, more solute) until the concentrations become equal.
Two bags of different strength
A thin membrane separates a weak sugar solution from a strong one. Sugar cannot pass through it, but water can.
Which way will the water mostly move?
- From the weak (dilute) side to the strong (concentrated) side
- From the strong side to the weak side
- It will not move at all
Watch the levels
Pick how much solute is on each side. Then slide time forward.
Osmosis
Water moves from a dilute solution (more water, less solute) to a concentrated solution (less water, more solute) through a selectively permeable membrane, until the concentrations become equal. This is osmosis.
Osmosis is diffusion of water across a selectively permeable membrane. In plants, water from the soil enters root cells by osmosis.
- Dilute side | Concentrated side
- Water | more | less
- Solute | less | more
- Water moves | leaves | arrives
Notes
Osmosis: water moves through a selectively permeable membrane from a dilute to a concentrated solution until the concentrations are equal. In plants, root cells take in soil water this way.
Check yourself
In osmosis, water moves…
Osmosis stops (no net movement) when…
Osmosis is best described as…
Left side has 2 units of solute, right side has 6. Together there are 12 units of water. When concentrations become equal, how many units of water are on the right?
Answer: 9
Equal concentration means solute and water share in the same ratio. 2 : 6 splits 12 into 3 and 9, so 9 units are on the right.
- from dilute to concentrated solution — correct. Yes. It moves toward more solute and less water.
- from concentrated to dilute solution. That is the wrong way round.
- only if the membrane is removed. Osmosis needs a selectively permeable membrane.
- the concentrations on both sides become equal — correct. Yes.
- all the water has left. It stops when the two sides match.
- the membrane dissolves. The membrane stays.
- diffusion of water across a selectively permeable membrane — correct. Yes.
- diffusion of solute with no membrane. That is diffusion in general.
- movement of cells through the soil. Osmosis is movement of water.