I am going to use Microsoft excel to draw an XY scatter diagram to display my results and draw a line of best fit I am going to use an Microsoft excel because it would be of greater accuracy and a lower margin of error.
I am going to record my results in table, I will use a results table with these headings like this.
Safety points
Use cork borers over tile on the table to reduce risk of slipping
Wear safety goggles to stop potato from flicking in eye.
Fair test
To make this a fair test I am going to:
- keep potato chips in solution for same period of time
- use the same size cork borer
- use the same quantity of solution
- use the same molarity of solution for each repetition.
I can work out the amount of cell sap in the potato from my line of best fit. The point where my line crosses the X axes in where the solution is isotonic with the solution in the cell. Any points below the X axes the solution is hypertonic to the sugar in the cells. Points above the X axes the solution is hypotonic to the sugar in the cells.
Apparatus
Boiling tubes, boiling tube rack, measuring cylinder, stop clock, digital balance, cork borer, scalpel tile, sucrose solution, and beaker.
Apparatus diagram
This is how I am going to set up my apparatus.
Method
- Cut the potato into 35 chips using he cork borer.
- Rinse and pat dry.
- Weigh potato chips individually then find the mean.
- Measure out the quantities and right molarity of solution.
- Put the solution into the boiling tubes and place boiling tubes in rack.
- Put potato chips into the solutions and leave for an hour.
- When the hour passes remove potato chips from boiling tubes.
- Pat potato chips dry and weigh.
- Record results.
Method for making correct solutions
I am given 2 mol/dm³ solution, I had to weaken this solution to get the right strengths for me experiment the table below shows the percentage of sucrose solution to de – ionised water. This is how I am going to control the concentration variable.
Prediction
I predict that the chip in the most dilute water solution will have greatest rate of osmosis, therefore the diameter will increase. The chip in the highest concentration diameter will decrease. I feel this will happen because of osmosis, the movement of water from an area of high concentration to low concentration I believe the cell will eventually turn turgid as it will begin to swell. The cells in the sugar solution will decrease in mass because the most concentrated solution will decrease in mass because it will loose water by osmosis the low concentration in the cell moving into the concentrated solution making the cell turn flaccid and the cell will shrink.
Bibliography
Conclusion
The results of the experiment show how the theory of osmosis works- the passage of water from a higher concentration to an area of lower concentration. My results were consistent and accurate to what i expected. On the graphs all of the lines stay on a straight line reinforcing the reliability of my results. I found that the graphs I produced were similar to the ones I researched. From my results I found that the concentration in side the potato cells was 0.4 mol/dm³this can be shown by my line of best fit. Where the line crosses the “X” axis is where the concentration is isotonic with the sap in the cell.
The potato chips in the higher concentration solutions diameters enlarged, potato chips in lower concentrations of solutions diameters got smaller. The reason this happened is because of osmosis, in the higher concentrations of solution the water moved into the potato chip because the potato chip had a higher concentration sap than the solution surrounding it. In the lower concentrations the water in the potato chip moved into the solution because the solution was more concentrated that the sap inside the potato chip cells.
Evaluation
My results were accurate and this was shown in my results. If I was to do the experiment again, I would improve the experiment by making sure the temperature remains the same throughout the experiment, put a cork in or cover tops of test tubes to stop evaporation so quantity of solution doesn’t lower and I could of weighed the potato chips to get more results. My results could have been unreliable because the experiments weren’t taken on the same day and I used I different variety of potato so there could be different rates of osmosis in different potatoes, temperatures may have varied over the different days, solutions and sizes there could have been some human error when measuring out solution and cutting potato chips.
To test osmosis further I could place a low concentration solution in Viskin tubing and place the Viskin tubing in a high concentration solution and see the water level raise inside the Viskin tubing.