Osmosis

Created by

Lily Tucker

Cards (11)

What's the aim of the practical?
To investigate the range of concentrations of salt or sugar solutions on the mass of plant tissue
What's the procedure?
Prepare samples of potatoes (or other plant tissue) and place in different concentrations of sugar or sodium chloride (salt) solution
Make measurements of mass and length of your samples before and after soaking them in solutions
Calculate the percentage change in mass of plant tissue
Plot, draw and interpret appropriate graphs
What should you do carefully and accurately in this experiment?
In this practical, you should take care to prepare your samples of potato carefully and record your measurements accurately
What solutions should this experiment be carried out with?
This practical can be carried out with either salt or sucrose solutions of at least five different concentrations
What will vary in this experiment?
The length of time that the potato cylinders are left will vary
E.g. This experiment can be carried out in a water bath at 30 °C in 30 minutes
Process
boiling tube process
What is the independent variable?
concentration of salt or sucrose solution in mol dm3
What are the dependent variables?
mass and the length of each potato cylinder before and after it has been submerged in solution should be measured
percentage change in mass and length will be calculated using these measurements
What are the control variables?
type and volume of solute in solution
temperature
time
Analysing the practical
Analysing the osmosis practical
How to analyse osmosis graph results?
Where results lie above 0 on the X-axis, this means the potato has increased in mass and taken water in from the surrounding solution, via osmosis
Where results lie below 0 on the X-axis, this means the potato has decreased in mass and water has been lost from the potato, via osmosis
Where the line crosses the X-axis, this is the concentration of sugar/salt inside the potato and no water has been lost or gained at this point