Preliminary Work:- In our preliminary work we used a partially permeable membrane, which in this experiment was Visking Tubing, filled with a sugar solution. In the top of the Visking tubing we placed a tube, then placed it in a beaker of water. The water molecules diffused into the Visking Tubing through Osmosis, because the sugar molecules in the Visking Tubing are to large to pass through the partially permeable membrane the contents of the tubing gets larger and the solution makes its way up the tube in the top of the Visking Tubing.
Method:- We will cut up 10 pieces of potato to the same length, which will be 3.5cm, there will be ten pieces so that we can do each strength twice. The potato chips will all be measured using the same ruler so if the ruler is out, all the potato chips will have the same amount out. They will all be taken from the same potato so we know the have the same water and sugar content. We will be uses the strengths: Distilled water, 0.2m, 0.4m, 0.6m, and 1.0m. Using test tubes we will put one piece of potato in each, then we will 6ml of solution to the tube. Then we will put them in a test tube rack and leave for 1 hour at the minimum to get the best results. If we leave it for to long the potato chips start to go rotten. We will take each one twice so that we can get an average.
Safety:- If we spill any of the solutions on the floor we will have to clean it up straight away otherwise someone could slip over on it and serious injure themselves. Also we should be careful when using the scalpel because it will be very sharp.
The results table we will Use:-
Obtaining Evidence
Aim :-To find out what happens when potato chips are put in different strength sugar solutions.
Prediction and Hypothesis :-Same as in the plan
Method :- As Planned
Length Of Potato Stick
Equation to work out the average = Try 1 After x Try 2 After / 2
= Average After
Analysis
Scientific Explanation :- Osmosis is the movement of water across a partially permeable membrane from a region of high water concentration to a region of lower water concentration. This happens in our experiment because; the outer layer of the potato chips is a partially permeable membrane. These have tiny holes in them, which only water molecules can get through. Inside the potato chips there are sugar molecules and a few water molecules. If we place the potato chip in a water solution because the water molecules in the chip and in the water are bouncing around they are going to find there way through the holes. But because there are more water molecules on the out side in the solution there are going to be more molecules going through into the chip tan out of it, because of this the chip will increase in size. The sugar molecules are much larger and are unable to pass through the partially permeable membrane.
From looking at the graph and the table of results I can see that Osmosis has taken place in this experiment. I know this because if we look at the distilled water we can see that water molecules have moved through the partially permeable membrane of the potato chips in to an area of lower water concentration, we can tell this because the chip has increased in length. Then if we have a look at the 0.6m concentration we can see that this chip has decreased in length, so again we can see osmosis has taken place because the water molecules from inside the potato chip have more from the high concentration of water molecules to the lower level of concentration.
Evaluation
Our experiment on the whole was a success with no problems all the way through. As far as we can tell our experiment was scientifically sound. We didn’t have any major anomalies in our set of results, but we did have a few off the line of best fit. If you look back at my graph you will see that there are two, the 0.4m and the 1.0m, these could have been caused by, us not measuring them as accurately as we did with all the other ones, these two could have had less solution than the other ones or they could have been a different size to the other chips.
I think that in this experiment we should have had a continuous concentration level, by this I mean that it shouldn’t of gone: Distilled water, 0.2m, 0.4m, 0.6m, 1.0m. There should have been a 0.8m in there to give us more accurate readings. We can predict from our graph what it should be but that is exactly an accurate way of doing it.
To follow up this experiment with another experiment I would do the same thing again but this time I would use more concentrations, they would be distilled water, 0.1m, 0.2m, 0.3m, 0.4m, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0m. This would give us a more accurate reading. Also to get a more accurate reading I would do each one 5 times to get a much better average over all 5. I would then plot these into the same table as I have done is this experiment and then draw to different types of graphs, to get a better look at my results.
