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The aim of this experiment is to investigate how changing the concentration of a solution will affect the rate of osmosis. I intend to use different glucose solutions as my variable and potato cylinders as my living organism.

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Introduction

COURSEWORK Introduction: The aim of this experiment is to investigate how changing the concentration of a solution will affect the rate of osmosis. I intend to use different glucose solutions as my variable and potato cylinders as my living organism. Hypothesis: I predict that the higher the glucose concentration is, the lesser the potato would weigh. This is because the potato contains more water than the glucose solution therefore it leaves the potato and goes into the solution in an attempt to even up the concentration on each side of the membrane. Biological Knowledge: Osmosis 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. A partially permeable membrane is one with very small holes. They are so small they can only allow water molecules to pass through unlike bigger molecules such as glucose. An example of a partially permeable membrane is a Visking Tube. The water molecules actually pass both ways through the membrane. Because there are more on one side than the other there's a steady net flow into the region with fewer water molecules for example into a stronger solution (in this case glucose). This causes the region with a lot of glucose to fill up with water. ...read more.

Middle

These also must be taken into consideration where safety is involved. * Make sure the solution is not taken internally - If so then contact a physician immediately * Remove anything that might be an obstruction - coats, bags, scarves, hats, books etc. * Tie back hair - the risk of getting your hair involved in the chemical reaction is decreased when you tie it back. Method: Tie back any loose hair or clothing Remove all bags and coats from the area you are working to minimize the obstruction Gather apparatus (as shown above) Label the test tubes using the masking tape Use borer to cut potato into cylinders Use the knife to make all the potato cylinders the same size Weigh each potato piece and record weight Measure 7ml of each solution Fill the test tubes with the different concentrations of glucose solution. Add potato pieces to solutions at the same time (fair test) Start stopwatch Leave for 40mins - 1 hour After 40mins - 1 hour remove from solution Weigh again and record weight Work out difference Work out the change in mass This a prediction of how I think my results will look: PRELIMINARY Results: As a table Concentration Weight (Before) ...read more.

Conclusion

This proved that osmosis had taken place whereas in the other three solutions plasmolysis had taken place. Both the results for my finale were similar and so I have the confidence that I have got accurate results. I have no regrets except continuously spilling the solutions all over the place and delaying my experiment. I did not notice any patterns that influenced my results. Evaluation: I learnt that there are many factors that can influence osmosis including temperature, time and concentration as was demonstrated I my experiment. On the whole, the purpose for doing a preliminary was achieved because I found out that there are certain things that I needed to change for the finale. I found that doing the experiment the second time was very easy because I had done the preliminary firstly. I has sufficient evidence to support my prediction and say that as there is more water molecules in one membrane it's mass will decrease due to the diffusion of water molecules. It would have been interesting to see how osmosis would occur in different membranes. I would have liked to try it out with a different vegetable like a carrot or cucumber for example. I would have been able to observe whether here is any relation to the experiment that I just done. Biology - Osmosis Mrs. Connew ...read more.

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