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
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:
* 6 test tubes
* 6 different concentrations of sucrose solutions
* Potato cutter/core
* Digital measuring scales
* Measuring cylinders
* Test tube racks
* Tissue paper
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. 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...
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