An experiment to investigate the effects of sucrose solution on Osmosis in potatoes chips.

Fair Test:

If I am going to keep this a fair test I must keep the following the same

• Temperature – Room Temperature
• SIZE of potato – 5cm
• Light intensity
• Volume of solution potato chip is in – 20ml
• Type of potato
• Time left in solution – 1 hour
• Surface area of potato chip
• Use the same balance to measure chip
• Same size test tube
• Same size potato bore

Safety:

To ensure safety, the boiling tubes will be kept in beakers so that they can not be knocked over. The potato chips will be cut on a white tile with a scalpel so that no one will be cut. Also while using scalpels everyone will have to wear safety goggles.

Apparatus:

The apparatus I will be using are:

• Stop Clock - to time our experiment
• Cutting tile - to cut the potato on
• Knife - to cut the potato
• 25cm Measuring cylinder - to measure the solutions
• Distilled water - part of the experiment
• Sucrose - part of the experiment
• Potatoes - part of the experiment
• Tissue paper - to dry the potatoes after the osmosis takes place
• Balance - to weigh the potatoes
• Cork borer - to cut out potato cylinders

Method:

We did a pre-test which gave us inaccurate results due to the fact that the solutions had been kept in the fridge over a week and because temperature affects the rate of osmosis we had to do another test to get accurate results.

We got 6 test tubes, two test tube racks and placed the test tubes inside the test tube rack according to the concentration of the solution. We got a potato and cut 6 cylinders using a potato borer. We then measured all the potato cylinders to 4cm and cut them using a knife and cutting tile. After this we measured the mass of the 6 potato cylinders and write them down on our results table. After each potato cylinder was measured we placed them next to the test tubes. After the potatoes had been measured and weighted we filled the one test tube with distilled water and then the rest in sucrose solution according to the concentration of the solution. We then put the potato cylinders into the solutions in minute intervals to allow all the potatoes to be put into the solutions and the same time, therefore keeping it a fair test. After all the potatoes had been put into the solutions we waited an hour before taking the potatoes out. We took the potatoes out in minute intervals to allow all the potatoes the same time. Each potato was taken out of the solutions and then wiped with a paper tissue to absorb all access water. Once the potatoes were wiped we weighted each one and write the answers down in our results table.

Results:

 

I have calculated the average masses before and after being in the solution (to 1 D.P) for 1 hour, and I also calculated the average percentage change in mass (to 1 D.P)

Conclusion:

As shown in the second graph the distilled water solution gains a mass of 5.8%. The 0.2 molar solutions has a gain of 6.3%, which is unusual because it shows that there was a higher concentration of water in the 0.2 solution than there is in the distilled water solutions, which we is incorrect because there is sucrose in the 0.2 molar solution and just water in the distilled water solution. For the 0.4 molar solutions there was no gain in mass. There has been a very rapid fall between the 0.2m and the 0.4 m solution which could have been because by the wrong substance being placed in the 0.2m solution. There has been a 3.2% decrease in mass for the 0.6m solution. This continues to decrease for the 0.8m solutions which have decreased by 9.9%. The last solution (1.0m) has decreased a total of 23.2%.

        The reason for these changes in mass is osmosis. This is also because the rate and direction of osmosis is different at different concentrations. When there was no sucrose present (distilled water), the water concentration is higher on the outside of the potato cells, and causes the water to osmose through a partially permeable membrane due to the concentration gradient. This is shown at concentrations 0.0 and 0.2, where water was gained. This causes the cells to become turgid.

        At the concentration 0.4m the point is on 0 on the graph which means there was no increase in mass or decrease in mass, this is known as an isotonic solution.

        At the 0.6, 08 and 1.0m solutions there was an increase in mass. This is because there is a greater concentration of water inside the potato cells then there is outside the potato cells. Therefore water osmoses out of the cells. This decrease in water causes the cells to become plasmolysed.

        The line in my second graph firstly that there is an increase in mass, which increases even more due to an error which happened while experimenting. The line then falls to 0.0; this shows that there was no change in mass, which means that the 0.4m solution was isotonic. The graph then falls rapidly for the 0.6, 0.8 and the 1.0m solutions. This analogy is as the sucrose concentration increases.

        The graph does not support all of my original predictions that I stated in the planning.

Evaluation:

In my opinion the experiment was not a total success. This is because of an error in the 0.2m solution. However I obtained a large quantity of very accurate results from which I was able to create informative graphs. I think I took enough results for the amount of concentrations that I was using, and the time that I used for the experiment to last was enough to allow sufficient osmosis to occur. However if I was to repeat the experiment I might well increase the amount of concentrations so that I can collect more accurate results. I might also change the producer I used to see if it is more accurate to collect information from a different producer.

        The method I used to perform the experiment was very simple, which made it easy to perform and collect data from the experiment. However I might decrease the number of people in my group because it is easy to give 2 people 2 jobs each which they could easily get on with, than to have 4 people doing 1 job and getting in each others way which could case inaccurate data. There was only one problem with my experiment which caused me getting inaccurate results. This may have been caused by a group member. When the potato chips were removed from the test tubes and dried I may well have dried some potatoes more thoroughly than others and so some would have more excess water, which would add to the mass. If the experiment was repeated I could find another way to dry the potatoes that would ensure that all were dried in the same way for the same time. However I think that the experiment was truly successful and I was very pleased with the complete comparison of my results with my initial prediction.