Prediction
I predict that as the concentration of sucrose solution increases, the potato chip after 24 hours will decrease in mass and length. I can make this prediction knowing how osmosis works. When there is a high sucrose concentration it will be greater than that inside the potato cells. This means the water from the cells will diffuse into the surrounding solution balancing the water and sucrose concentration. As the cells loses water through diffusion, the potato chip becomes plasmolysed, making the chip collapse, which causes the chip to change in mass and length. The above can also be reversed when the concentration in the potato chip is greater than the surrounding solution. Instead of the water diffusing out, it diffuses into the cell causing the chip to become turgid, making the potato chip swell. We can use the principle I have explained to find out the concentration of the potato cell: when there is no change in mass or length we know that no water has diffused in or out, this means the concentration of the sucrose is equal to that inside of the potato chip.
Diagram Here
This diagram explains the experiment we are carrying out, when the solution outside the cell has a greater concentration than the cell inside.
After obtaining these results I realised they weren’t good enough and I hadn’t enough time to record and obtain all the sucrose solutions I said I would investigate. So from now on I will be using the results I obtained in class to analyse and plot up my graph.
Analysis
Our results show that as the concentration of the sucrose solution increased the smaller the potato chips got. This proves my earlier prediction. This happened because osmosis was at work. Water from high areas of concentration diffused to areas of low concentration. As the concentration of sucrose increases the amount of water in the solution decreases. This means water from the potato chip diffuses into the surrounding solution which is sucrose. Thus the cells become plasmolysed and the chip decreases in mass and length. The above can also be reversed when there is higher concentration inside the potato chip than outside. The water diffuses into the potato chip making it turgid; therefore the potato increases in mass and length.
Graphs here
The graph I have plotted is the percentage change in size of potato chips against the concentration of sucrose. I have drawn lines of best fit to exploit trends in our results.
Using the graph we can find out the osmotic potential of the potato cell (which sucrose concentration doesn’t lose or gain water, size or mass.) we find this out by finding the point that both lines of best fit cross the X-axis. Because both the mass and length lines don’t cross at the same point we must estimate the point on the line between the two. In this case 0.305m is the reading between both the lines of best fit. So the osmotic potential of the potato chip is 0.305m.
Evaluation
I think the investigation went fairly well and although the results were not precisely accurate, they were good enough to prove our hypothesis and what we believed would happen. The potato would decrease in mass and length when the sucrose concentration was high outside of the potato chip, and high inside the potato chip. There are some points for the experiment we should look over and if we do the experiment again we should take into consideration in order to get better results.
The point we should take into consideration are:-
- Firstly we should take numerous tests to find a more accurate average
- Use more and wider range of sucrose solutions
- We did not take the potato chips out at the same time allowing some chips more time in the sucrose; this could have affected the results. We should have done each test one at a time to give us a more fair result.
- Although estimating the osmotic potential was ok for this investigation, it would have been better and more scientific to work it out properly. The two point the lines of best fit crossed in the graph were 0.28 – 0.33,
the range = 0.05 so the point exactly in the middle is 0.28 + ½ of 0.05, which
is 0.28 + 0.025 = 0.305, so I was right the first time.
Other areas we could investigate could be to select a different root vegetable
such as an onion, we could vary the sucrose solution concentration these are
all possibilities, simply vary the variables.
Overall I believe the investigation went vary well, proving what we were
Investigating.