Before planning the experiment, I will research osmosis, so that I can make predictions. This will help me to discover how to make this investigation fair and safe. Planning ahead will help me find out the order in which to carry out the experiment. This should lead me to good results at the end of the experiment.
Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. When a potato is placed in water, the cells will expand by gaining weight depending on the concentration levels of the solution. When the concentration of the water is lower, more water molecules are allowed to pass through the potato cell. This causes the potato to gain weight and expand. If the concentration levels of the solution are higher, the cells will lose water and cause the potato to lose weight and therefore shrink.
I predict that when the lower the concentration of sugar solution in the water, the more the potato will expand by osmosis. When the concentration of water is identical to the concentration of the potato cell, there will be no increase or decrease in weight. This is because the amount going into the cell will be the same as the amount going out. As soon as the water concentration becomes higher, the cells will shrink because more water will be leaving the cell than entering it.
In distilled water alone, I predict that the water in the potato will be more concentrated. Because of this, the water should transfer from the solution to the potato, and the potato will gain weight.
In the 0.2 molar solutions, the substances will be very similar in concentration. There should be little change to the size and weight of the potato.
When the potato is placed in 0.4 molar solutions, the substances will still be very similar but the concentration of the water solution should be slightly greater to that of the potato. This will cause the potato to shrink slightly.
As the molar solutions get higher, the water will transfer more and more from the potato to the water solution, therefore decreasing its size and weight. The most extreme shrinking should occur when the potato is placed in 1.0 molar solution, as here the difference in the water concentration is at its largest.
I will be using a very sharp knife, which could injure someone if it is not handled properly. And I will also be careful that the solutions do not get into my body internally as I am not fully aware of the damage it could cause.
I will cut chips from the same potato because different potatoes may act differently and affect the results. I will cut them 15mm long exactly with square ends 5mm wide and 2mm thick. I will use a chopping and knife for this. They all need to be exactly the same size to ensure that it is a fair test. I will weigh the chips to ensure that they are the same size and weight. This will also give us a measurement to compare them to afterwards. I will use three identical potato chips in each solution. This is because the experiment may not go to plan. If we have three chips, an average can be taken at the end of the experiment to obtain more accurate results. The three potatoes will be placed in 6 different solutions, 1.0 being the strongest and distilled water being the weakest. The solutions I will use are as follows:
0.0 (Distilled water)
The boiling tubes will be placed in a rack with an equal amount of molar solution. This is because identical solutions are needed for it to be a fair test. The potatoes will be covered with the solutions, if not the water will not be able to pass in and out and the potatoes would dry out. The solutions will all need to be the same temperature and the chips will need to remain in the test tube for the same length of time. The length of time I have chosen to keep the potatoes in the solution is 5 minutes. This should be enough time for the osmosis to take affect. When the potatoes are removed from the solution, the osmosis stops. I will then dry the potatoes using a paper towel being careful so that none of the potatoes fall apart. I will place them into sets of three depending on when which solution they were placed in and weigh and measure them. To get the most accurate results, I will take the average reading of the three pieces. I will then analyse my results and see if they match my prediction.