Analysing results
The investigation cannot be based on changes in mass from just one potato cylinder.
Percentage changes in mass must be calculated for each cylinder. A The mean is calculated by adding all of the data and dividing by the number of items of data. value for the change in mass of potato cylinders at each concentration 鈥 measured in moles of A disaccharide made from glucose and fructose. It is used as table sugar. per dm3 of Mixture formed by a solute and a solvent., or mol dm-3 鈥 should be calculated.
A graph is plotted of change in mass, against concentration of sucrose.
Where potato cylinders have gained in mass, the change will be positive.
Where potato cylinders have decreased in mass, the change will be negative.
| Concentration of sucrose | Average change in mass (%) |
| 0.0 | +26.8 |
| 0.2 | +5.0 |
| 0.4 | -7.7 |
| 0.6 | -17.9 |
| 0.8 | -26.0 |
| 1.0 | -31.4 |
| Concentration of sucrose | 0.0 |
|---|---|
| Average change in mass (%) | +26.8 |
| Concentration of sucrose | 0.2 |
|---|---|
| Average change in mass (%) | +5.0 |
| Concentration of sucrose | 0.4 |
|---|---|
| Average change in mass (%) | -7.7 |
| Concentration of sucrose | 0.6 |
|---|---|
| Average change in mass (%) | -17.9 |
| Concentration of sucrose | 0.8 |
|---|---|
| Average change in mass (%) | -26.0 |
| Concentration of sucrose | 1.0 |
|---|---|
| Average change in mass (%) | -31.4 |
Where the line crosses the horizontal axis at 0 per cent change in mass, the sucrose concentration is equal to the concentration of the contents of the potato cells. Therefore, the concentration of the water in the outer solution is equal to the concentration of the water inside the cells.
This can be identified on the graph as the point which shows no change in mass, and therefore represents no Overall. movement of water by osmosis.
Question
What is the concentration of solutes in the cells of the potato in this investigation?
0.27 mol dm-3.
This value is where the line crosses the x-axis.