B1 Flashcards
What is Osmosis?
Osmosis is the movement of water molecules across a partially permeable membrane form a region of higher water concentration to a region of lower water concentration
What can pass through a partially permeable membrane?
only tiny molecules e.g water
What happens in the membrane during osmosis?
the water molecules pass both ways, this happens because water molecules move about randomly all the time
What happens when there are more water molecules on one side than on the other?
There will be a steady net flow of water into the region with fewer water molecules i.e the stronger sugar solution
What happens to the strong sugar solution during osmosis?
It gets more dilute, the water tries to even up the concentration on either side of the membrane
What test can you do to show how osmosis works?
Potato cylinder
What is the FIRST step of the potato cylinder experiment?
- cut up a potato into identical cylinders and get beakers with different sugar solutions in them from pure water building up to very concentrated sugar solution
What is the SECOND step of the potato cylinder experiment?
- measure the mass of the cylinders then have one cylinder in each beaker and leave for 24 hours
What is the THIRD step of the potato cylinder experiment?
- take out the potato, dry it and measure it again
What is the FOURTH step of the potato cylinder experiment?
- if cylinders have been drawn in by osmosis, they’ll have increased in mass, if water has been drawn out, they will decrease in mass, calculate percentage change in mass
what is the dependent variable of this experiment?
the mass of the chip/potato
what is the independent variable of this experiment?
the concentration of the sugar solutions
what are the control variables of this experiment?
volume of solutions, temperature, time, type of sugar used
