How much does osmosis occur when a potato slice is place in a test tube with a sugar and water solution?

However if the concentrations on both sides are equal the same amount of molecules will be moving in both directions causing equilibrium.

Fair Test

In order to keep this experiment as fair as possible we will keep a number of factors the same:

) The weight and size of the potato discs Diameter =7mm

Height =10mm

Weight =0.50g

2) The volume of the different concentrations Volume =20cm²

3) The time allowed for osmosis to occur Time =3days

4) The amount of potato discs in one tube Amount =3discs

However we will change:

) The concentrations inside the tubes.

Safety

As safety is a large factor whilst collecting results during practical sessions we will make sure all members attending will wear, eye protective goggles and protective gloves to stop any dangerous solutions making contact with the skin, or accidents with cutting tools

Pre-Test

We will carry out a pre-test to make sure that this experiment is possible.

Concentration (m)

Weight after experiment (g)

0.0

0.59

0.1

0.56

0.2

0.54

0.3

0.50

0.4

0.48

My conclusion is that as the concentrations change the amount of osmosis changes. This proves to me that this experiment is possible.

Apparatus

Test tubes

Beaker

Measuring cylinder

Potato

Cork Borer

Balance (scales)

Scalpel

Bungs

Protective gear

Test tube rack

Diagram

Method

. First we will gather our apparatus and set it up as shown below

2. Secondly we will use the cork borer to cut long slices out of the potato. Then, using the scalpel and the balance, cut the potato so it weighs exactly 0.50g and measures exactly 7mm in diameter and 10mm in height.

3. We will then get the test tube rack and put in 5 test tubes and label them with all the different concentrations. Then put 20cm² of the corresponding solution in the test tube.

4. After this we will put three slices of the potato into each test tube and put a bung on the top and leave it for 3 days.

5. After 3 days we will take the bungs of the tops and take the pieces of potato out of the solution and dab any excess solution from the outside. We will then weight each one and record the results in a table.

Results

Concentration

(m)

Weight after osmosis (g)

AVE

Percentage increases

2

3

0.0

0.59

0.56

0.65

0.60

20%

0.1

0.58

0.58

0.62

0.59

8%

0.2

0.54

0.56

0.54

0.55

0%

0.3

0.44

0.58

0.50

0.50

00%

0.4

0.48

0.46

0.47

0.47

-6%

Percentage Increase

Percentage increase = Increases x 100

Original Mass

Conclusion

Having looked over my Results I have notice that my hypothesis was correct. I found that osmosis takes place in a concentration where the solutions are not balanced on either side of a semi-permeable membrane, and that it takes place more when the concentrations are very different.

When we increased the concentration we could see that less osmosis took place until I looked at the results for concentration for 0.3m and there was no net affect and the average showed that no osmosis occurred and the results for concentration 0.4 showed that water had left the potato and it was lighter than when we started. This proves to me that the concentration between sugar and water inside of a potato is 0.3m

I noticed that there was one irregular result in my experiment. That was the result for 0.3m test one and test two they were both very different to the reliable result and they did not follow the pattern of the experiment. The fact that there were two irregular results in the same concentration tube say two me that they were probably touching in the test tube and as a result of this there was a different amount of surface area showing and not the same amount of osmosis was able to occur.

Evaluation

This experiment was a fairly easy one to follow. However if I were to do this experiment again I would try to use a broader range of concentrations. This would give me a wider view of what sort of weight increase or decrease osmosis is capable of, and maybe try and get a very high percentage increase. I would also use a balance to three decimal places. Also I would measure my potato slices out more accurately. This would give me a more accurate reading as to how much osmosis is taking place.

During this experiment I found out that the extent of osmosis is much larger than I though as I felt that it would be hard for the particles to pass through what looked to me like a membrane that was totally waterproof

I would improve my investigation by making it more accurate. I would use visking tubing in a broad range of concentrations and a computer to read the weight change over a period so the computer could show me when osmosis is occurring the most. I would use visking tubing as it can hold larger amounts of solution and so more osmosis would take place and so a more obvious weight change would occur. As an extension to this, I would also measure the length and depth of the pieces of potato so then I would see if there was any size change as well as weight change. I could also use different potatoes to see if there is a difference in concentration between potatoes.