Osmosis.

Introduction:
Osmosis is a net diffusion of water between two solutions that differ insolute concentration and that are separated by a selectively permeablemembrane.
Hypertonic solution - higher solute concentration outside the cell.
Hypotonic solution - lower solute concentration outside the cell.
Isotonic solution have the same solute concentration outside and inside thecell.

Hypothesis:
Potato cells in 0% solution of salt will swell up. Potato will gain weight,because net movement of water will be into the cells. Water moves down theconcentration gradient.
Potato cells in 2% and 3% solutions will shrink. Water moves out of thecells to regions of greater solute concentration.
Potato cells in 1% solution will change little in cell size or shape. Thedifference between solution concentration and potato concentration issmall. So there is no big movement of water.

Materials: Knife, potato, 4 salt solutions (0%, 1%, 2%, 3%), paper, razorblade.

Method:
Cut 12 plugs from similar potatoes. Remove the ends of each plug and skin.
Make up four solutions of salt (0%, 1%, 2%, 3%). Weight the plug sets.
Place plug sets into each solution and continue to measure or weight themat specified time intervals. Report mean values only fo measurements orweights. Determine the percent change in lenght or weight for the potato ineach solution. Calculate the exact percent of salt in the potato cell fromthe graphed data.

| Salt | Initial | Weight of plug sets after some | Mean |
| Solution | weight | time: | percentage |
| s | (g) | | change in |
| | | | Weight |
| | | 12 min. | 22 min. | 40 min. | 52 min. | |
| 0% | 5.61 | 5.87 | 6.01 | 6.13 | 6.25 | 11.4% |
| 1% | 8.84 | 8.85 | 8.87 | 8.90 | 8.86 | 0.22% |
| 2% | 10.02 | 9.61 | 6.51 | 9.20 | 8.99 | -10.3% |
| 3% | 6.64 | 6.01 | 5.77 | 5.48 | 5.31 | -20% |

We can't compare the changes in weight using grams, because each plug sethad different initial weight before placing them into salt solutions.

Conclusion and evaluation:
From the graphed data the percent of salt in the potato cell is 1.1%. Theoriginal potato cell concentration is 0.9%. The error could be, because thewater outside potato has influence on weight and not accurate measurementof mass by not exact scales, which showed only one decimal place.
If the concentration of water is not equal across a potato cell membrane
(concentration of water outside the sell is more or less than 0.9%),osmosis tends to occur. Water will move osmotically to regions of greatersolute concentration (from hypotonic to hypertonic solutions). If waterconcentration outside and inside the cell is equal, water shows no netosmotic movement from one to the other - isotonic solutions.
The experiment can be improved: Firstly, by drying potato from wateroutside the potato. Secondly, by using scales, which have more accuracy.