Investigating the effect of different concentrations of salt solutions on osmosis in potatoes

The apparatus used in this experiment were:

• 4 beakers
• 4 test tubes
• 4 pipettes
• 4 pieces of potato without skin (all the same size)
• 20ml of distilled water
• 20ml high concentration salt solution
• 20ml medium concentration salt solution
• 20ml low concentration salt solution
• Scales
• Knife
• Cork borer

Firstly I collected and set up all the equipment I needed, I then added 20ml of high concentration salt solution to a clean and dry beaker; this was repeated with the medium concentration salt solution, low concentration salt solution and distilled water, and these are the independent variables. I used a cork borer to cut out four pieces of potato which I then measured and cut with a knife to ensure that they were all the same size. I recorded the weight of each piece of potato after weighing them on the balance. One piece of potato was then added to each solution in its beaker and left for fifteen minutes to allow osmosis to occur. After fifteen minutes, I removed the pieces of potato from the solutions and once again recorded their weights, finally I calculated whether the potato pieces had gained or lost weight. To ensure that my experiment was reliable I took great care in measuring the lengths of the potato pieces, thus assuring that the surface area of each piece was similar, I used the same amount of solution in each beaker and I also used the same type of beaker for each solution therefore the surface area covered for each piece of potato was similar.

In conclusion, I found that the lower the concentration of salt in the solution, the greater the weight of the potato. This is because osmosis occurred more in the low salt concentration solution than in the high salt concentration solution, therefore more water moved into the potato in this solution, as a result of this the change in weight of this piece of potato was greater than the others. The potato in the high salt concentration solution lost weight because the concentration of water was higher in the potato, therefore the water molecules moved out of the potato into the solution causing the piece of potato to lose weight.

The hypothesis I made matched the conclusion I came to therefore I think the results I collected were fairly reliable and accurate. As I was unable to repeat my experiment, I compared the results I collected to the results that others collected, however this may not help with the reliability of my experiment as the other students may have conducted their experiments in different methods therefore obtaining a variety different results making it invalid.