Investigation the Water Potential of a Root Vegetable

When the water potential of the surrounding solution is less negative

than that of the potato cells, water enters the cells’ vacuoles by

osmosis causing the turgor of the cells to increase.

Method

1. Using a cork borer remove a core of potato.

2. Use a white tile to push the cork borer into the potato.

3. Using a scalpel or razor blade cut the skin off the ends of the

potato cores.

4. Cut the potato cores into 30 disks 5mm thick, using a ruler to

measure the thickness.

5. Place the disks into a petri dish to prevent the evaporation of

water

6. Make different concentrations of sucrose solution 0.1, 0.2, 0.4,

0.6, 0.8 molar and distilled water. Place the solutions into a water

bath to keep then all at the same temperature.

7. Remove 6 disks at a time from the petri dish and weigh them using

an electronic balance. Record the weight of the potato chips. Then

place in each different solution.

8. Shake solutions every 10 minutes. After 1 hour remove the disks

from the solutions, blot dry and reweigh.

9. Then repeat the experiment 3 times so an average of results can be

taken to give a more accurate result and show any anomalies.

Independent variable-Different solutions

The independent variable in the experiment is the different

concentrations of solution.

I am going to make the following solutions using salt and water.

0= pure water

1= NaCl (salt)

1 mole= Relative molecule mass (g) dissolved in 1000cm3 of water

58.5g (NaCl) in 1000cm3 water = 1 molar solution

5.85(g) in 1000cm3 of water = 0.1 moles

So therefore:

0.1molar = 0.585(g) in 100cm3 water

0.2molar = 0...

... middle of paper ...

... out more clearly if there

were more repeats, and the longer the chips are left in the longer

there is for osmosis to occur.

However I do feel that the experiment was carried out to a suitable

degree of accuracy. As when I cute the potato chips I put then all

straight into a petri dish to ensure that no evaporation occurred.

Furthermore, all of the potato chips were left in the solutions for

the same amount of time. In addition to this when I was making up the

salt solutions I used a graduated pipette to measure the solutions

which provided very little chance of human error in measurement.

Finally, the percentage change was calculated to plot the graph to

make the experiment a fair test.

If I were to repeat the experiment I would take the above points into

account to make the experiment as accurate as possible.