Osmosis in Potato Cells

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Ben Zaré 9MK Biology Investigation - Osmosis in Potato Cells 9/7/04

Section 1 – Planning

What is the aim of your experiment? What do you want to find out? The aim of this experiment is to investigate how potato tissue changes when placed in sucrose solution of different concentrations. Therefore, I want to find out if and how osmosis differs, when the concentration is changed.

What is the variable you are going to change in the experiment? The input variable of this experiment (i.e. the variable to change) will be the concentration of sucrose solution present in the test tubes, which the potato samples will be placed into.

What is the variable you are going to measure in your experiment? The output variable of this experiment (i.e. the variable to measure) will be the mass and length of the potato sample, before and after osmosis has occurred.

What are the other variables in your experiment? How can you keep them constant? The variables to be controlled in this experiment are: the total amount of sucrose solution used, the size and shape of the test tubes used, the type of water used (in this case, it will always be distilled), the potato tuber used to collect potato samples (for one particular set of results), the length and circumference of the cork borer used the type of weighing machine used (i.e. how many decimal places it measures to).

What apparatus are you using? What is this piece of apparatus for? How does it work? Why did you choose it? How accurate is it?

•A potato tuber of a certain size and variety, to obtain all of the potato samples for one particular set of results. •A cork borer to obtain samples of a certain circumference from the potato tuber, which can then be cut to a uniform length. •Test tubes (6 for each set of results) to store the distilled water and sucrose solutions (of different ratios) in, after they have been measured out correctly. Then the potato samples can also be added to the test tubes. •Labels will be stuck on to each of the six test tubes; to indicate what ratio the solution is in. This will make it easier to record results correctly and avoid mistakes. •A scalpel will be needed to cut the samples, from the cork borer to a uniform length. •A separate measuring cylinder will be used to measure the correct amounts of sucrose solution and distilled water (to avoid contamination). These measured amounts can then be added together, in a test tube. •Sucrose solution (360g/dm³) will be added in certain ratios to distilled water, inside test tubes. •Distilled water will be added to sucrose solution, in certain ratios, inside test tubes. •An electronic weighing machine (giving the mass to 2 d.p) will be used to measure the mass of the potato samples, before and after the experiment. •A test tube rack would be used to hold each of the six test tubes.

Write in simple steps a list of instructions you are going to follow in your practical. Make sure they are clear so other people can follow them. Explain why you are doing each step.

1.Firstly, the apparatus listed, above, would be gathered.
2.The six test tubes would then be placed into the test tube rack, securely, so that they are easily accessible but will not tip over or roll off the surface that will be worked on. 3.Next, the sucrose solution would be measured out six times in one of the measuring cylinders (each time, the appropriate amount of sucrose solution would be emptied into one of the test tubes and a label, with the number 1 – 6 would be placed on the appropriate test tube, indicating which solution is which). 4.The previous process would then be repeated with the distilled water, using the second measuring cylinder. The end result will be six test tubes, each labeled, with an equal total amount of solution. The solutions required for the experiment would now be prepared. 5.Next, the cork borer (with diameter 3mm)...
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