Prediction
In my experiment my prediction is that the lower the concentration of the sucrose solution the higher the amount of increased mass of potato chip. I think that the mass will increase because of the process of osmosis.
Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.
The potato has a low concentration of water whilst the solutions have a high concentration (although this is varied). Because of water potential osmosis allows water into the potato. The semi permeable membrane only allows water molecules through (in this case not glucose) this is because the holes in the membrane are very small and can only physically fit water molecules through because they are much smaller then glucose ones.
When the solution is dilute the water molecules are freer to move and therefore more likely to pass through the semi permeable membrane. Whilst in the concentrated solution the solute molecules attract some of the few water molecules leaving only a small percentage free to move. When the water molecules attract to the solute molecules they form a hydration shell.
The higher the kinetic energy with in the water the more likely the molecules are to hit the cell membrane. When the do collide with the cell membrane it creates pressure called water potential.
It is very important to insure that the level of precision is very high within the experiment. All sorts of precautions need to be made to make the results as accurate as they can be. Examples of precautions-
I am using special apparatus to insure precision such as measuring cylinders to measure accurately. I am using top pan balance to record my results to 2d.p . I will be trying to blot the potatoes of excess water before I weigh them but I will have to be careful not to reverse the osmosis process that has just taken place by letting the paper towels soak up too much water. Finally I am going to have to make sure that the potato chips are submerged within the solution for the same period of time so that the experiment is accurate.
When taking the precautions just mentioned and being generally careful when performing the experiment the results should be reliable. One way to insure reliable results is to take repeat readings and then obtain a average reading. It is likely that I will get anomalous results on the overall trend but I will try to find a cause or explanation for each one.
I have done some preliminary work and research also. I have learnt about osmosis and I have done an experiment involving a high glucose solution and some viscing tube (which is a semi permeable membrane.) This gave me a basic knowledge of which solutions I would need and which equipment was most suitable for my experiment I then extended my knowledge by doing some preliminary results by performing the actual experiment. Here are the results
In order to find the percentage mass change I did the simple equation
The initial preliminary results would coincide with my prediction.
Obtaining Evidence
Safety is a very important factor within any experiment and this includes insuring certain precautions and measures are taken to protect anyone from getting hurt. For example:-
- Always wearing goggles to protect your eyes especially when dealing with chemicals.
- Putting lids back on chemicals and solutions as quickly as you can to try and prevent spillages.
- Being extra careful when using knifes and scalpels.
- Keeping the working area clear from clutter to avoid accidents.
I did the experiment and got two sets of results to allow for any anomonous results.
Here is a table of my results:-
Results A
Results B
From these results I have now found a average percentage mass change by taking the relevant result from table A and table B and finding the average.
When collecting these results I used a variety of processes to insure they where accurate for example a consist level of blotting the potato chips so that the amount of excess moisture removed was fairly equal. And also used accurate equipment to insure the measurements where accurate when measuring the amount of solution.
Someone using the same equipment and accuracy is likely to get similar results. In order for it to be a true fare test there should only be one variable and everything should be kept the same.
My graph has shown that potato chips loose mass at higher concentrations and gain it at lower concentrations of sucrose solution. This we know is because of osmosis and water potential. The higher the concentration of the solution the less amount of water molecules there are to go through the semi permeable membrane into the potato therefore increasing the mass. The lower the concentration of the mass the more water molecules there are to increase the mass of the potato. The results on my graph are very consistent of a pattern and contain a negative correlation. If one point has to be recognised as slightly anomonous it would be 0.8 it is very slightly off the line of best fit. The anomolous origin of the point is from results B where the point is contradicting the pattern but in the main averages graph the result A has evened the value out. The line crosses the y-axis at approximately 0.5 so this is the predicted equilibrium. It is expected that at this point there would be equal water potential levels and therefore no molecules would be exchanged. The graph defiantly proves my prediction to be right.
Evaluation
I feel that overall the experiment went well. My measurements were accurate and as my graph would show my precautions paid off. There are many ways that I feel my method could be improved for example a more precise way of controlling the amount of moisture lost when blotting the chips of excess water. Also being able to insure the quality of the solution. This we were unable to do. We believed and hoped the solutions were of a good quality but could not prove or ensure it. I probably would have got more accurate results and have been able to prove my theory about sucrose solution at concentration 0.5 if I had a higher range of concentrations such as 0.1, 0.3, 0.5, 0.7, 0.9. If I had taken more sets of results I would have been able to have maybe produced a better explanation for my anomalous result in results B(0.8 concentration). Overall I have enjoyed the experiment and am happy with the results.