Method
The investigation is very straightforward.
There won’t be any control for this experiment, because the weight would vary depending on the potato pieces. And therefore, it might affect the results, which we are going to take in after the experiment.
First I will have to get the pieces of potatoes ready. I will push the cork borer through the potato, cutting it into long cylinders with a diameter of 6mm. And then I will cut the potatoes into cylinders of 40mm, and weigh 6 sets of 3 potato cylinders. I will have 6 sets because we will have to test the potatoes in 6 different types of solutions; 5%, 10%, 15%, 20%, and 30% solutions of sugar, and distilled water.
I will weigh each set and have them ready for us to put into the test tube.
Then we will put the 6 sets of 3 potatoes in the 6 test tube at the same time and start the clock running for 20 minutes.
After 20 minutes, we will take all of the potatoes out of the test tube, so that the actual osmosis action stops, and we will put the potatoes onto one piece of dry towel, in their own groups. We will dry them with the tissue paper, in sets of 3, and weigh and measure the potatoes taking in the average reading of the 3 pieces.
We will repeat the experiment three times so that we can make sure that all our results are similar, and so that we will be able to take the average of the 3 experiments. This makes sure that we get accurate results. Repeating the experiments is important, because we will be able to receive valid results, and look for any anomalous results.
Fair Test
If I am going to make this a fair test, then I will have to control these factors. Doing the tests at one fixed temperature will control the temperature of the water. For the purpose of my experiment I am going to do all the experiments at room temperature.
The size of the potato is very important. This is because if the size of the potato varies, so will the amount of mass it can loose or gain. I am going to try to cut all the pieces of potatoes, to the same size. Because of the 'chipper´ I will have chips with the same width but the length of the chips will differ. I am going to cut the chips to 3cm in length.
The mass of the potato is a variable, and this means that it will be measured throughout the experiment. I will measure the mass in grams. The potato chip will be measured before it is put in the solution, and after. This will allow us to see whether osmosis has taken place, and how much osmosis has occurred.
The volume of the solution that the potato chips are kept in must be the same. The chip must be totally covered in the solution, and the amount of solution will be kept the same because all the chips are the same size. The amount of solution I cover each chip in will be 30ml.
The type of potatoes I will use is going to be kept the same, because different potatoes may absorb at different rates. For this experiment I am going to use the same potato.
The time the potato chip is left in the solution must be kept the same for each chip. This is because more or less solution may be absorbed depending on time. I am going to keep each potato chip in each solution for nine days.
The surface area of the potato chips will be kept the same by having all the chips the same size. This must be kept the same because the amount of surface area exposed to the solution may affect the rate of osmosis. The thickness of the chip will already be the same, so I will cut the length of each chip to 3cm long.
To make the mass readings fairer, I will take each chip, roll the chip gently on a paper towel, to remove all excess solution, and I must not squeeze the chip.
I am also going to use the same balance to weigh my chips. This is because the measurements may vary slightly between scales.
Apparatus
- 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
- Sugar solutions - 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
- Potato borer - to cut out potato cylinders
Analysis
The graph shows a line going from top left to bottom right. It is a strong negative correlation. As the concentration increase the mass decreases. For the concentrations’ 10%, 5% and 0 %( distilled water) the mass of the potato increased. For 15% the mass stays almost the same with just a tiny increase. For concentrations’ of 20% and 30% the mass decreases. 15% is the equilibrium
Evaluation
We followed the plan correctly; I believe we gained accurate and sufficient enough results to conclude the experiment, and to prove our hypothesis.
My final results were very reliable, due to the precautions I took to make this a fair test. I think I took enough results for the coursework. The range of results was big enough. Also to make my experiment more accurate I could have repeated it more. I could have also cut the potatoes into slices, to give a larger surface area for osmosis to occur on.
I could extend my coursework by testing the chips using a different substance. By this I mean using a different thing instead of sugar, i.e. salt or coffee. Then I could find out whether osmosis occurs differently with different things diluted in the water. I could even use different vegetables.
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