Osmosis in Different Concentrations

Topics: Osmosis, Concentration, Semipermeable membrane Pages: 10 (2433 words) Published: November 28, 2012
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 

* Potato cutter/core 

* Digital measuring scales 

* Measuring cylinders 

* Knife 

* 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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