Osmosis in Different Concentrations
I am going to investigate osmosis when potato is placed in different concentrations of sucrose. I am aiming to witness osmosis in 5 different concentrations of sucrose. I will use 5 varying concentrations so that I have a wider spread to compare the results, and check that I don’t have any anomalies Prediction Osmosis is the process of diffusion of water molecules from a weaker solution into a stronger solution, through a semi permeable membrane.
The tiny pores in the membrane of the potatoes will allow the water molecules to go in and out of the potato cell, depending on the concentration gradient between the potato and the sucrose solution. If the water concentration is lower in the potato than in the sucrose solution, then water will pass from the sucrose solution into the potato, and it will gain weight.
If there is a higher concentration of water in the potato, then the water will go out of the potato and into the sucrose solution, as osmosis is the movement of water molecules from a region of high concentration to a region of low concentration, through a semi permeable membrane. So, I predict that the higher the concentration of sucrose, the lower the weight of the potato as water from the potato diffuses into the sucrose solution. Predicted graph of results: [IMAGE] Apparatus * 6 test tubes * 6 different concentrations of sucrose solutions * Potato Potato cutter/core * Digital measuring scales * Measuring cylinders * Knife * Test tube racks * Tissue paper Method I will need 1 piece of potato in each tube. As there are 15 tubes I will have to calculate how many pieces I will need altogether. I think this would be a suitable calculation: 1x15=15. So, I will pierce out some pieces of a potato using a core, and then cut 15 slices with a knife. Then I will measure 10ml of each of the 6 sucrose solutions using a measuring cylinder. I will be given these different concentrated solutions in the general laboratory.
Order custom essay Osmosis in Different Concentrations with free plagiarism report
450+ experts on 30 subjects
Starting from 3 hours delivery
I will label the tubes 1 to 15 and fill each one with 10ml of the solution. Tube 1-3 will have a concentration of 0 Tube 4-6 will have a concentration of 0. 4 Tube 7-9 will have a concentration of 0. 8 Tube 10-12 will have a concentration of 1. 2 Tube 13-15 will have a concentration of 1. 4 I will measure each slice on the measuring scales to identify each potato slice with its weight before and after immersion in the sucrose. Having measured each slice on the scale and recorded its weight, I will then place the slices in the test tube containing the solution for 24 hours.
Then I will empty the solution from the test tube by pouring it in the sink and remove the potatoes by hand and place them one by one on the scale. For accuracy, I will make sure that I wipe off any excess solution on the scale before placing each new slice on it. I will record the weight after placing them in the solution for 24 hours. This process will be repeated for tubes 1 to 15 and the results will be noted in a table and then plotted on a line graph. I will make this a fair test by only varying the concentration of sucrose and the size of the potato slices, but keeping everything else the same.
The same potato must be used for the whole experiment or otherwise, the results would differ as the age and sizes might be different, which means one potato might have more water in it than the other. I will use a 10ml measuring cylinder so that I can accurately measure the exact amount of sucrose needed. As the cylinder measures different sucrose solutions, it has to be washed out each time I measure another 10ml of sucrose for the next tube, because it may be contaminated with the different sucrose’s.
All the tubes will be kept for the same time, in the same place, so that the uncontrollable temperature would not affect the tubes separately. I will not be able to control: * Temperature – because I won’t be in the laboratory for 24 hours, and the temperature could change in the night, or morning. *Temperature of solution- because I was not able to obtain a thermometer and I was not in the laboratory for 24 hours so it could change. * Weighing scales – because these are digital and therefore, it produces results by itself. I will be able to control: Concentrations of sucrose – they are already measured * Time – I will do the experiment, and come back the next day at the same time, and promptly record the results *weight of the potato- I weighed the potato slices before the experiment. For safety in the laboratory, I will be very careful using the sharp knife which I will be using to cut the potatoes with. I will make sure that I have an overall so that my clothes don’t get dirty if the solutions spills. I will remember not to put potatoes or sucrose in my mouth as they might have been infected by chemicals in the lab, which are poisonous.
I will measure the weight of the potato in grams, and the concentration of sucrose in percentage. I am expecting everything to work out well as I have a perfectly good method but if I feel that the results may be wrong, I will repeat my experiment. Preliminary results These are my results: This experiment supports my plan and prediction. The carrot gains weight in normal water, and decreases weight in concentrated sugar solutions. By doing this experiment, I believe that my method is good, and it will work. I think I should specifically be aware of the scales, because they alter a lot.
However, this was carried out at home, so the cooking scales may have not been so accurate, as accuracy is not very important in cooking. Results these are my first results. They proved to be wrong. This mistake would have been made my human. I assume that I used two different scales, and have got all the weights jumbled up. The weight taken at the beginning is also not correct, so I may have made a mistake right from the start. Concentration of sucrose. | Weight before| Weight after| 0| 1. 28| | 0| 1. 33| | 0| 1. 29| | 0. 4| 1. 29| | 0. 4| 1. 27| | 0. 4| 1. 2| | 0. 8| 1. 31| | 0. 8| 1. 3| | 0. 8| 1. 3| | 1. 2| 1. 29| | 1. 2| 1. 37| | 1. 2| 1. 27| | 1. 6| 1. 26| | 1. 6| 1. 3| | 1. 6| 1. 31| | Conclusion I found out that as the concentration of sucrose increases, the weight of the potato decreases. In water it gained 1. 26 grams, but in 1 Sucrose solution, it lost 0. 16 grams. My prediction supports my conclusion. I have calculated the average change in weight to have a simple, clear idea where the experiment is leading me to. Instead of having a large number of weights, I combined them into one by averaging them.
I found the average by adding the weight gain/loss for each tube and divided it by three. To find the percentage, I multiplied that decimal by 100. I drew a line graph, and then a line of best fit, which is sloping downwards, negatively. This proves that the weight is getting lower as the percentage of the sucrose concentration is getting higher. In my investigation I found a definite relationship between the 2 variables – weight and concentration of sucrose. Any increase in sucrose concentration led to a decrease in weight. The prediction is supported by the evidence of the graph.
Although there is one anomaly, all the other results stand out and give a straight line of best fit – exactly as I predicted. The point of early plasmolysis is where the concentration of sucrose and potato are even. There is no osmosis taking place at that point. As I said in my plan, if the water concentration is lower in the potato than in the sucrose solution, then water will pass from the sucrose solution into the potato, and it will gain weight. If there is a higher concentration of water in the potato, then the water will go out of the potato and into the sucrose solution.
This is because osmosis is the movement of water molecules from a region of high concentration to a region of low concentration, through a semi permeable membrane. The up raise of sucrose is the downfall of potato mass. [IMAGE] Osmosis In osmosis, water diffuses through a semi-permeable membrane. This diagram illustrates the concentrated sugar solution, separated from dilute sucrose solution by a selectively permeable membrane. This has pores (holes) in it which are very small, and selects what it wants to let through i. e. small molecules.
Water molecules are very small. Each one is made of two hydrogen atoms and one oxygen atom. However, sugar molecules are many times larger. In potatoes, the pores of the membrane only let the water through. There is a higher concentration of sugar molecules on the right-hand side of the membrane in the diagram, than in the left-hand side. Sugar molecules would diffuse from the concentrated solution into the dilute one until they were evenly spread out if there was no membrane, but they cannot do this as the pores are too small for the sugar to get through the membrane.
Therefore, the small water molecules diffuse into the concentrated sugar solution, to make it more dilute. This process is called osmosis. It is the diffusion of water molecules from a place where they are in a higher concentration, to a place where they are in a lower concentration, through a selectively permeable membrane. Potato cells plasmolyse in concentrated solutions. This diagram illustrates a plant cell[IMAGE] (which is similar to a potato cell) in a concentrated solution. It will lose water by osmosis. The cytoplasm and the vacuole will shrink.
The cell membrane is semi-permeable and the vacuole contains a sucrose solution. So when a cell is placed in distilled water (high concentration) water will move across the semi-permeable membrane into the cell (lower water concentration) by osmosis, making the cell swell. This cell is called ‘turgid’. In potato cells, the cells would increase in length, volume and weight because of the extra water in the potato. If the potato was to be placed in a lower concentration, then the opposite would happen, because water would move out of the cell into the solution.
If the solution is very concentrated, then a lot of water will diffuse out of the cell. The cytoplasm and vacuole will keep shrinking, but the cell wall will not as it is too stiff. As the cytoplasm shrinks further and further into the centre of the cell, the cell wall gets left behind. The cell membrane, surrounding the cytoplasm, tears away from the cell wall. If this happens, the cell is said to be plasmolysed. The potato will therefore, decrease in length, volume and weight. Plasmolysis is the point where the membrane is totally detached from its ell wall, and the potato is killed. Evaluation my experiment shows some accurate results. It concludes the experiment, and proves my prediction. My final results were quite reliable; due to the precautions I took to make this a fair test. The graph has a straight slope pointing downwards, which is the clearest way to understand my prediction. All of them are not that closely together, neither far away, so a line of best fit joins some tips of the points, and causes it to go straight down.
I have one anomalous result, which falls on 0 on the x axis. This occurred in tube 5, which contained a concentration of 0. 4. Perhaps I did not carry out that properly. These were the main problems in carrying out the experiment:- * Scales kept moving * Difficult to get out the potato from the core * Potatoes get stuck in tube. * Solution is still left after wiping the potato and the scales * Different scales * couldn’t control the temperature the point of early plasmolysis would not be valid.
This is because I have just plotted it on the graph on a line which suits my results. To prove that it is the right point, I would have to do another experiment to find that out. The other evidence is likely to be valid, because as all the evidence links to the results. My investigation is fair because I did not change many things, expect the concentration of sucrose. I think that I have collected quite a lot of evidence to support my conclusion. The result table is the main source of evidence.
I could try investigating with more percentages of sucrose concentration, the size of the potato and have more short intervals between the sucrose’s. This would have a more spread to the results, and therefore, results can be compared and evaluated more thoroughly. They would be very accurate as well as reliable. As I have an anomaly, my evidence may not be extremely correct. I would have to do more research to what I have already done (in the conclusion) on osmosis, and see what actually happens, and see if it occurs in plant cells all the time.
If I were to repeat the experiment, I would use a very accurate scale, so that results would come out accurately and then I would have a accurate average. The graph will be fairly accurate. I would also make sure that the scale and the potato slices are properly wiped. This is because if they are not wiped, the weight would increase, and will not be accurate. I could use a syringe or a burette to measure the 10ml of sucrose solution, because those two apparatus are very accurate.
I would do several more experiments with bigger sizes of potatoes to obtain more evidence to support my conclusion. I will also do some research on osmosis, and this will make me certain of my evidence if I have many to compare with. I will agree with the majority. Overall, I am very pleased with these results and with the evidence I have so far, that osmosis occurs when there is a high concentration and a low concentration, both aside a semi-permeable membrane. The lower concentrated substance diffuses through the membrane to where there is the higher concentrated substance.
Cite this Page
Osmosis in Different Concentrations. (2017, Mar 06). Retrieved from https://phdessay.com/osmosis-in-different-concentrations/
Run a free check or have your essay done for you
