Osmosis will turn the potato chip, turgid. Turgidity is when lots of water gets in to the cell. The cell swells up and the cell membrane expands and stretches.
Sometimes an organism needs to move dissolved substances from a region where they are in Low concentration, to a region where the dissolved substances are in a higher concentration. This process is of course opposite to the direction of diffusion. This is known as Active transport. Active transport involves selective movement of certain particles. The particles move against the concentration gradient, so requires energy to do this.
In this experiment we need to find an area in which osmosis doesn’t occur. The concentration gradient we are aiming for looks like this.
So if osmosis takes place into the potato chip, it will cause it to go turgid, and gain in weight.
So we know that if after the experiment the
Potato chip weighed less it became flaccid,
Therefore osmosis has taken place out of the chip.
Diagram
Apparatus
I will need to use the following equipment for my experiment;
- Film canisters
- Salt solutions of concentrations, 0M, 0.5M, 0.75M, 1M, 1.25M, 1.5M
- 25ml measuring cylinder
- Potato
- Cork Borer- size 6
- Ruler
- Scalpel
- Balance
- Stopwatch
Fair Test
In my experiment I need to keep a few things the same so it is a fair test. I will need to keep the following the same,
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The amount of salt solution- because if we keep the amount of salt solution the same, we can compare fairly how the potato reacted with the different solutions.
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The mass of the potato chip-because if it is different each time the potato, will gain or lose weight according to the salt solution, so the weights will be totally different and it wont make the experiment fair.
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Using the same cork borer- because if we don’t use the same cork borer, each of the experiments, the potato will have a different surface area each time.
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The time in which the potato chip is in the salt solution- because if we leave the potato in the salt solution, each for a different time each potato would have a different mass depending on what salt solution and the time.
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2 potato cylinders in each canister- because if I do it for 1 experiment it must be the same for the others to compare, but it doesn’t effect the results, and it is a quicker experiment.
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Drying the potato cylinders of excess water- because if we don’t dry the cylinder of excess water so it doesn’t get taken into account for the mass of the cylinder at the end. We will shake each cylinder 3 times each.
Variable to be changed
The variable that I will change in this experiment will be the salt solution. I will use 6 different salt solutions. 0M, 0.5M, 0.75M, 1M, 1.25M and 1.5M.
Method
1.Use the measuring cylinder to measure 20ml of each salt solution into film canisters. Label the canisters with the salt solutions.
2. Use the cork borer to make potato cylinders and cut then into 12 pieces each 2g in mass.
3. Record the mass measurement in the table of results.
4. Put 2 potato cylinders in each of the canisters.
5. Leave for 20 minutes.
6. Take each potato cylinder out of the salt solutions and shake it 3 times to remove excess liquid.
7. Re-weigh each potato cylinder and record in the results table.
8. When you have done at least 2 experiments work out the average weight after and complete the table.
Results
Conclusion
As a result of this experiment, I found that as the concentration of the solution increases, the mass of the potato chip decreases. My graph and results shows and proves this.
The results show that osmosis took place in to the chip, causing it to go turgid, at 0M. At a concentration of 1.5M, osmosis takes place out of the chip, which causes it to become flaccid. We know this as when we weighed the chip at the beginning of the experiment, it weighed more than it did than at the end of the experiment we know it was flaccid, so when it weighed more after we know it went turgid.
So we had to find a concentration of salt solution needed to store a potato, so no osmosis occurs. From my graph, if we look at point X, this is when the potato doesn’t lose or gain weight. So a salt solution of 0.125M would be my prediction to store a potato.
Osmosis wouldn’t occur in 0.125M salt solution because the concentration of water molecules inside the potato would be equal to the concentration of water molecules on the outside, therefore there would be no concentration gradient for water molecules to travel down, which was my aim.
If I look at my graph, I see that the average % change in mass goes down in uneven jumps. I marked two points, labelled 1 and 2. Point 1 is at a concentration of 0.25 and the average % change in mass is –2.5, and at point 2, the concentration is 0.5, and the change in mass is –5.5. So without my graph, I wouldn’t have been able to predict what salt solution osmosis wouldn’t occur.
Therefore my prediction was incorrect. I predicted that the best solution would be 1M. I said earlier that the reason I would predict that would be because I needed to find a reasonable area been 0M and 2M where osmosis doesn’t occur.
Evaluation
I thought the experiment was easy enough to carryout because it was fairly straight forward, however there a few problems, which occurred. The problems I came across were little ones but seemed to affect my graph and results. So If I were to do the experiment again, I would try and improve it so the problems didn’t occur. So I found that I couldn’t always get the potato chip the right mass of 2g all the time, to improve this I would spend time and concentrate on making sure the potato is the right weight. Also the time, we put the potato chips in for 20 minutes and sometimes the time overlapped the 10-minute barrier so the chip had a bit longer in the solution. So to improve it I would concentrate more. All these mistakes occurred because we were limited for time, if we had more time and didn’t have to concentrate on other things, maybe the problems wouldn’t have been as big.
Due to these problems, they affected the results and the graph. When I looked at the graph I found that 2 points don’t sit on the curve of best fit. These anomalous results, a and b, came about because of problems. I think that if we had more scientific equipment, the experiment would have been more accurate and mistakes wouldn’t have occurred as much. Also if we had longer time in which to do it, we could of let the potatoes stay in the solution longer so we could see the results over a longer period of time.
