Osmosis Flashcards
What is osmosis?
Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
What is a partially permeable membrane?
A membrane with holes so small that only tiny molecules like water can get through.
Describe the movement of water molecules through a membrane.
The molecules go both ways because they move randomly. However, because the net flow is steady, water molecules flow into the region where there’s fewer of them.
Why does water still flow into a strong sugar solution, even if it’s more dilute?
Because the water is trying to make it even.
What is the first step of setting up a potato osmosis practical?
Cut the potato into identical cylinders. Get beakers with different sugar solutions, one should have pure water, one should be a very concentrated sugar solution. Other concentrations of other beakers can vary.
What is the 2nd and 3rd step of the potato osmosis practical?
2nd- measure the mass of the cylinders, then leave one cylinder in each beaker for 24 hours or so.
3rd- take them out to dry and measure their masses again.
What is observed in the potato osmosis practical?
Cylinders that have absorbed water by osmosis have increased mass. Cylinders that have not absorbed water by osmosis have decreased mass.
What is the dependent variable, independent variable and other variables in the potato osmosis practical?
Dependent variable- The mass of the potato.
Independent variable- The concentration of the sugar solution.
Other variables- Volume of solution, temperature, time, type of sugar, etc.
What are some errors that can occur in the potato osmosis practical? How can you reduce them?
- Potato cylinders aren’t fully dry.
- Excess water would give a higher mass.
- Water evaporation.
You can reduce these by repeating the experiment and calculating the mean.
