Diagram.
Apparatus List.
- Cutting tile
- Borer
- Scalpel
- Electronic scales
- Measuring cylinder
- Test tube x 18
- Test tube racks
- Tweezers
Plan.
In the experiment I will cut 18 chips from a potato, using a borer and scalpel, making sure that each chip weighs 1.5 grams. I will then measure out 75 ml of each concentration of salt solution at room temperature into 18 test tubes, and placing them in a test tube rack I will then add a potato chip to each solution. I will then leave the potato chips in solution for 2 hours.
On removing the potato chips from their solutions I will immediately weigh each one, recording the change of mass, if any, of each chip.
Key Factors
To keep this a fair test there are many factors that we must keep constant. We must leave all the potato chips in the solution for the same amount of time, as the potato chips left in longer would gain or lose more mass than a chip not left in for as long. Each solution must also be the same temperature. If a solution is hotter then the molecules move about faster, causing more collisions and therefore osmosis to occur quicker. If we are to use more than one potato, all potatoes used must be exactly the same, as different types of potatoes with different textures will act differently.
If the surface area of one chip is bigger than another then this will affect osmosis, as osmosis can occur quicker through a larger surface area than through a smaller one. We must also keep the volume of solution constant; infact the only variable will be the concentration of the solution, as we want to see what affects this has on osmosis.
Preliminary Results.
Prediction
From the results of our preliminary experiment above, we can make a fair prediction as to how concentration affects osmosis. It seems from the table above that a potato in water will gain mass, while a potato in salt solution will lose mass. From this I can predict that the higher the concentration of the solution, the greater the loss of mass in the potato.
Results
Conclusion
From the previous graph it is clear that as the concentration of salt solution increases, the more the mass of the potato chip decreases. This is because more water molecules must leave the potato chip to make the salt solution less concentrated, and the potato chip more concentrated. The diagrams below show the difference in molecular activity in the less concentrated solution to that in the higher concentrated solution.
As you can see from the diagrams above, it will take much longer, and many more water molecules to balance out the concentration in the more concentrated salt solution. My final results are very similar to my preliminary results, in that the higher the concentration, the greater the loss in mass. It seems that from my preliminary results I made an accurate prediction as to what would happen in terms of osmosis.
