Find out if changing the concentration of a sugar solution affects the mass of a potato.

Prediction:

I predict that as the molarity of the sugar solution increases the loss of mass will happen because there is more sugar on the outside of the potato and the water inside the potato will need to escape through the membrane of the potato to dilute the sugar solution. I have also chosen to do this because in my prelim experiment when I did the chopped potato the greatest mass loss was in the highest sugar solution. I also think that the potato will lose more mass because there will be less water in the cells of the potato and water weights a lot so this will affect the weight of the potato. I also think at the point that I cut the potato it will lose mass because when I am cutting the potato it is losing water because the cells will be damaged or cut in half so water will be able to escape.

Risk assessment:

Don’t drop the test/boiling tubes because they could break and the glass could end up cutting someone. Also be careful when using a scalpel because there are sharp and you could cut yourself.

Step By Step:

1. Firstly collect all the apparatus and set up ready to do the experiment.
2. Core the potato and then chop it up into 4 equal pieces of 1cm each. Then weigh each piece and record the weight.
3. Place these into 6 separate test/boiling tubes.
4. Measure out exactly 25cm³ of the sugar solution for each concentration (0.0m, 0.1m, 0.2m, 0.4m, 0.8m, 1m.)
5. Put the solution into the correct tube and label it with its molarity.
6. Repeat the results 2 more times in hoping to get a set of reliable results.
7. The next day gather your test tubes. Then weigh them on the weighing scales and record in a table of results.

Apparatus:

• Test/Boiling tube – I will use this to keep my solution and pieces of potato in.
• Potato – I will chop this up and use it to check the weight loss when its placed in different solutions of sugar.
• Weighting Scales – I will use this to check the before and after weight of my pieces of potato.
• Test tube rack – I will use this to hold my test tube and boiling tubes in.

(Table of results in on file paper)

Analysis:

Overall in my graph which I have produced from my results supports my prediction in saying that as the concentration increases the mass will decrease. For most of the concentrations the mass decreases as the concentration increases. I think that the mass decreased as the molarity of the solution increased because the water level was less in the solution the higher the molarity because their will be more sugar in the solution. So for this to change the potato needed the water to go through the membrane at a higher rate. The procedure is called osmosis. This means that when the sugar solution is at a balanced rate of water/sugar solution the potato will stop letting out water and the piece of potato will weigh less than it started. I have also noticed a pattern. The variable of the solution affects the mass of the potato in the end. Also I think that the solution could be replaced with surface area in this pattern because it would affect the final mass because there would be more water in the one piece of potato.

Evaluation:

In the end my results were not good but at the same time some were very good. They weren’t very good when it came to drawing a graph though. I couldn’t get a decent line of best fit so I changed some of the results slightly. I found two anomalies in my graph. They were the averages for 0.1 and 0.2 molar. I think these happened because I don’t think that the chopped pieces of potato were all exact same lengths so this would have changed the surface area of some of the pieces. They were meant to be 1cm each and there was meant to be 4 pieces. Another factor was that when I was measuring the solution out I never measured it from the bottom of the dip in the meniscus point. This would mean that there was more liquid in some of the tubes than in the others. To improve my experiment I would get someone to check that I am cutting accurately and not to much or to little. I would also like to use a glass measuring cyclinder because they are clearer to read off than a plastic one and therefore they are more accurate as well. Another point is that when I was drying the surface of the potato I was using a paper towel and they can absorb more of the water out of the cells out the potato and this would effect the level of osmosis in the solution and then the potato sample would probably turn brown because of the lack of water in its cells. This also means I was taking to much water out of the potato, to improve this I would use something else that would take off the surface water and not water out of the cells. I would probably use something like cling film and I would roll it along the cling film to take off the surface moisture.