Maths - Calculating percentage gain and loss of mass in osmosis
Analysing results
The investigation cannot be based on changes in The amount of matter an object contains. Mass is measured in kilograms (kg) or grams (g). from just one potato cylinder. In scientific tests, we must ensure a number of examples are used to allow for A result that is unusual or unexpected. results and variation.
Percentage changes in mass must be calculated for each cylinder and The mean is calculated by adding all of the data and dividing by the number of items of data. calculated.
A graph is plotted of change in mass, in per cent, against The concentration of a solution tells us how much of a substance is dissolved in water. The higher the concentration, the more particles of the substance are present. of A disaccharide made from glucose and fructose. It is used as table sugar.. Concentrations of solutions are shown as percentages. A larger number means a higher concentration.
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 | +26.8 |
| 20 | +5.0 |
| 40 | â7.7 |
| 60 | â17.9 |
| 80 | â26.0 |
| 100 | â31.4 |
| Concentration of sucrose % | 0 |
|---|---|
| Average change in mass (%) | +26.8 |
| Concentration of sucrose % | 20 |
|---|---|
| Average change in mass (%) | +5.0 |
| Concentration of sucrose % | 40 |
|---|---|
| Average change in mass (%) | â7.7 |
| Concentration of sucrose % | 60 |
|---|---|
| Average change in mass (%) | â17.9 |
| Concentration of sucrose % | 80 |
|---|---|
| Average change in mass (%) | â26.0 |
| Concentration of sucrose % | 100 |
|---|---|
| Average change in mass (%) | â31.4 |
Where the plotted line crosses the horizontal axis at 0 per cent change in mass, the sucrose concentration of the solution 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 The overall effect of something when all additions and deductions are calculated. movement of water by The movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration., which would be represented by a change in mass.
Question
What is the concentration of The dissolved substance in a solution. in the cells of the potato in this investigation?
29%
This value is where the line crosses the x-axis.