An Explanation of the Theory of Osmosis

Aim My aim is to find out the percentage increase or decrease in mass (grams) of potato tube, placed in varying concentration of glucose. Prediction I predict that the potato chip will decrease more in mass in the stronger glucose solution. The Scientific theory of Osmosis Osmosis is a special case of diffusion which involves water. Basically it 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. This means that only water molecules can pass through the partially permeable membrane due to it being small enough to fit through. Bigger molecules such as glucose would not be able to get through. Also Osmosis makes plant cells swell up.

* Apparatus The apparatus which I am going to use are: 5 test tubes, a scalpel, a sensitive balance, a cork borer, a square tile, and a glass rod. Factors The factor which is going to change is the amounts of glucose being put in each potato chip. There will be 5 test tubes. In the first one there will be distilled water, which contains 0% glucose. The amount of glucose in each test tube will go up by 20%, all the way up to 80%. So it will be 0% (distilled water), 20%, 40%, 60% and 80% of glucose. The factors which are remaining the same are the initial mass (grams) and the room temperature.

Measurements To conduct an experiment with accurate results as possible, appropriate measuring equipment will be used. The sensitive balance will be used to weigh each potato chip before and after it has been placed in certain amounts of glucose. Each result is going to be compared with another result because the experiment is going to be done twice in order to get better and more exact results. Method 1) I first collected all my apparatus needed for the experiment. 2) Get the cork borer to make potato tubes. Then with the scalpel roughly make the same size, not forgetting to do it on the square tile. 3) The sensitive balance is used to get the exact mass for each potato chip. If some of the chips are more dense than the others cut a bit off. For extra safety use a tile underneath while cutting the potato chips to make them all equal mass by using the scalpel. 4) All 5 potato tubes will then be placed in individual test tubes, which are filled with different amounts of glucose. The first potato chip will be placed in distilled water which has 0% glucose. The other 4 potato tubes are placed in glucose with the amounts starting from 20% going up to 80% glucose. 5) Use the glass rod to stir the glucose/distilled water which should be in the test tubes, along with the potato chip to make the experiment work better. 6) Leave the potato chips for 30 minutes in the test tubes. 7) When 30 minutes is up, take the potato chips out and use a paper towel to absorb the excess glucose/distilled water which will be dripping off it. If this isn´t done it would effect the results by making the potato chips heavier when coming to weigh it. 8) The sensitive balance will be used to weigh all 5 potato tubes. Don´t forget to record the results. 9) Repeat the experiment again to obtain accurate results and compare with the original. Diagram Results See results table and graphs

Analysis (See graphs page) On trial 1 the graph shows the percentage increase/decrease of the mass of the chips. By looking at it, the mass increases at 0% because glucose is not present. But as the glucose concentration is increased the mass of the potato chips decrease. Out of all 5 potato tubes, 60% of glucose is the point where it loses most of its mass. At 80% of glucose the 5th chip doesn´t loose as much water as the previous one did. This shows that only a certain amount of water can be taken out of the potato until it reaches a point where no more can be lost. In this case, its peak is at 60%. On trial 2 the first 3 readings are similar to trial 1. I´ve noticed that around 40% concentration has reached the maximum percentage decrease.

The last 2 results look strange because at 60% the reading should of been approximately -20 grams. The result of potato chip weight at 80% concentration should of been the lowest but it´s similar to 40% concentration. This may have occurred due to inaccurate results. The last graph shows the Average Percentage increase/decrease in mass of the potato for trial 1 & 2. This looks right because the highest reading is at 0% which shows that the potato tube is at its heaviest due to having no glucose. Conclusion I predict that the potato chip will decrease more in mass in the stronger glucose solution, has proven to be right. The reason for this is because that osmosis will make water molecules move from a high water concentration to a low water concentration. All my graphs show that stronger the glucose concentration the lighter the chip is in mass (grams). The pattern which I´ve noticed is that all my graphs generally form a slope when joining up all the points. Also I have learnt that the water from the potato chip can only be absorbed a certain amount then it stays the same mass like in trial 1. Evaluation In trial 1 the graph looks totally fine. It looks that 60% glucose concentration is its peak decrease out of all the potatoes. That may of happened because that certain chip may have more water to release then the others, or 60% is the maximum amount that the potato tube can work best to decrease in mass. In trial 2 the last 2 results look weird. I think the reason for this is because my method was not good enough. When filling each of the test tubes with glucose, I did not use a measuring cylinder to measure the required amount. I just poured until the glucose solution covered half of the test tube. That may look same in all the test tubes but I might of added extra or less to it. To improve my method I would definitely use a measuring cylinder next time in order to receive a high standard of results. I would also improve the range of glucose concentration. Instead of it going in 20´s, I would prefer to have the glucose concentration in 10´s, up to 100. This way you have a vast variety of readings to look at. When I do another experiment I am going to plan my method in advance in order to be more organised, that way less inaccurate readings will happen and it will make everything run smoothly and efficiently. Overall I found this experiment challenging, educational and fun.