Osmosis
This practical lesson covers:
- How to investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue.
Investigating osmosis using potato cylinders
Aim:
To investigate the effect of a range of concentrations of salt or sugar solutions on the mass of potato cylinders. This will allow you to determine the concentration of the cell sap of potato cells.
Background information:
Osmosis is the diffusion of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration. In this practical, you will investigate how varying concentrations of salt or sugar solutions affect the mass of potato cylinders.
Variables:
- Independent variable - concentration of the salt or sugar solutions
- Dependent variable - change in mass of the potato pieces
- Control variables - volume of solution, temperature of the solutions, time in the solution
What is the independent variable in the osmosis experiment?
the length of the potato cylinders
the percentage change in mass of the potato cylinders
the concentration of the salt or sugar solutions
the mass of the potato cylinders
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What is the dependent variable in the osmosis experiment?
the density of the potato cylinders
the length of the potato cylinders
the percentage change in mass of the potato cylinders
the concentration of the salt or sugar solutions
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What is the purpose of recording the mass of each potato cylinder?
to calculate the percentage changes for each cylinder
to compare the results with distilled water
to determine the length of each cylinder
to measure the volume of each cylinder
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What is the purpose of using distilled water in the osmosis experiment?
to dilute the salt or sugar solutions
to clean the boiling tubes
to measure the mass of the potato cylinders
to compare the results with the salt or sugar solutions
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What should be done after removing the potato cylinders from the boiling tubes?
rinse them with distilled water
measure their length using a ruler
blot them dry with paper towels
record their mass accurately
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