Method
Eight potato chips were cut using a sharp scalpel and a ruler to exactly 40-mm in length. Before the potatoes were put into the different concentrations of the sugar-water solution, the beakers were labelled saying what beaker would contain which concentration.
The potato chips were then put in 1, 0.6, 0.4 and 0.2 molar concentrations of sugar solution. The sugar solution contained 20ml of water. Finally a potato chip was put into distilled water. All of these potato chips were placed in the water precisely at the same time as each other to make the experiment as accurate as possible. The experiment was timed for 20 minutes. The test was then repeated. The changes in length of the chips were recorded.
Safety
Ensuring an adequate safe working area is necessary when using a scalpel and the glass beakers.
Planning
Variables that are going to stay the same
Measuring cylinder
Ruler
Volume of solution
Time of chips in solution
Temperature
Variables that are going to change
The concentration of the sugar solution
The measuring conical and the ruler are going to stay the same, because this type of equipment is mass-produced. It would be inaccurate to use different rulers and measuring conicals each time the test is done, during the experiment.
The concentration of sugar solution is going to change so the prediction can be proved or disproved.
Results
solution length at start length after 20 mins change in length average
(Molars) (Millimetres) (Millimetres) (Millimetres) (Millimetres)
Test 1 Test 2 Test 1 Test 2 test 1 test 2
1 40 40 38 39 -2 -1 -1.5
0.6 40 40 40 39 0 -1 -0.5
0.4 40 40 40 40 0 0 0
0.2 40 40 40 41 0 1 0.5
Distilled 40 40 42 42 2 2 2
Analysis
The results were pleasing. The graph shows a negative correlation between change in length against sugar solution. The graph proved the prediction. The prediction was based on a scientific theory called 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.
If a potato chip is surrounded by water, the water particles in the potato will naturally diffuse into the potato chip, by osmosis, making the potato chip bigger. If there is a rich sugar solution surrounding the potato chip, the water particles in the potato will naturally diffuse out of the potato chip, by osmosis, making the potato chip smaller. If the concentration of water in the potato chip is the same as the concentration of water outside of the potato chip, there will be no change in length; this is called the isotonic point of concentration.
There was an isotonic point of concentration shown on the graph, which further backed up the prediction.
Evaluation
Although the results and graph proved that the prediction was correct, there were lots of ways that the experiment could have been improved; a more constant temperature in the room (temperature controlled room), more readings at longer timed intervals, and a bigger potato chip size. All these things would have made the experiment more accurate.
