Investigation to see what effect different concentrations of solution has on osmosis

* The pieces of potato must be the same width and length, as they must have the same surface area given to the solutions. This means that if one cylinder is given more solution than another cylinder, then the one with the larger surface-area, will have a larger contact with the solution. Therefore the thought of osmosis occuring could be affected. This would then affect my results invalidating them.

* The weights must also be as accurate as possible. When the balance is being used, before each potato cylinder is placed on the scales the scales must be set to 0.

* There must be equal amounts of solution in each test tube. This again is to with how much solution the cylinders are exposed to. As this could again affect the rates of osmosis.

* All the pieces must come from the same potato. If I used a different potato, the second potato may have a higher or lower solute concentration.

* All the pieces must remain in the solution for the same amount of time. If one pieces of potato stayed in the solution longer than a different one then it would have had more time for osmosis to occur. This could lead to false results.

* I will have to keep the potatoes and solutions at the same temperature (room temperature in this case)throughout the experiment.

Method

. Set up the apparatus required for the investigation.

2. Cut three pieces of potatoe chips, from the same potatoe.

3. Cut them to the exact same width and length.

4. Weigh the pieces till all three weigh the ame. To do this I will have cut the excess pieces, till it's the same weight.

5. Get 15ml of each solution, and pour them in the three test-tubes, as written in prediction. Test tube 1, will be for rich sugar solution, test tube 2 for 0.5 Molar and test tube 3 for pure water solution i.e 0.0 Molar.

6. Put the three pieces of potatoes in a different test-tube.

7. Then time for ten minutes.

8. After ten minutes, sieve each solution out, dry the cylinders aand then weigh to get new results.

9. Repeat the procedure three times, nad record results.

Results

Potatoe Chip

Weight Before Reaction (Exp1)

Weight After Reaction (Exp1)

Weight Before Reaction (Exp2)

Weight After Reaction (Exp2)

Weight Before Reaction (Exp3)

Weight After Reaction (Exp3)

A (1Molar)

3.23g

2.97g

.91g

.67g

.62g

.22g

B (0.5Molar)

3.23g

2.98g

.91g

.64g

.62g

.25g

C (0.0Molar)

3.23g

3.24g

.91g

.66g

.62g

.44g

Conclusion

The conclusion I have come to is that rich sugar solution has the most effect on potatoe chips, in losing weight. This proved my hypothesis. I tried the best in keeping all variables the same. Doing the experiment three times, however wasn't the best idea as I couldn't do graphs to support my results and come to a clear conclusion, which could have been easier to see if there were graphs.

Evaluation

I did the experiment of which several faults were recognisable to me, after starting the reaction. For example I didn't dry all the cylinders equally on the tissue paper in the first experiment, which could have affected the weight. If I were to do the experiment again, I would make sure I don't make the same mistake again. I realised the mistake after I looked at my results. The water solution only gained in weight by 0.01g, whereas the others gained weight by a lot more. My thought was that I dried every other one with care. Also, the cuts I made in the potatoes to identify them were difficult to see when the pieces of potato shrunk and were taken out the testtubes. This could have given me false results.

Something else I think which could have caused some results were due to using the same ppotatoe chips after two or three days.

If the experiment were to be done again, I would be more careful with all the variables and do the expeiment more than three times.

Apart from all these, I think that the experiment was satisfactory.

OSMOSIS COURSEWORK BIOLOGY

TAHSIN SIDDIQUI