I am conducting this biology investigation to find out whether the weight of the weight of a potatoes changes whilst put into different strengths solutions of water and salt. The weight of the potato will change due to a process called osmosis.

Method

I will cut a potato into five chip-liked slices. I will try and cut them to equal size but that doesn’t really matter because I am measuring the average weight increase or decrease not heather the potato chip expanded or contracted in width or length. I will them peel the skin off potato pieces this is because the skin is not on all the potato chips and the skin may affect osmosis making my results unreliable. I will then measure use the measurement below, using two 5cm3 syringes, one for the distilled water and another one for the salt.

I will full up five test tubes with the different concentrations of the solution. Then I will place the five potato chips into the test tubes simultaneously and leave them in the test tube rack for 30 minutes. I am leaving the potato chips for that length of time because I feel that is long enough for osmosis to take place and show a sufficient if any weight change in the potato.  I will then take the potato piece out of the solution, and plot each piece on tissue paper this is making sure that water not absorbed by the tissue is not weighed. I will then repeat this experiment once more and then using my results work out the average weight change of each concentration of the solution. I will do the experiment twice to make my results more accurate and therefore more reliable. Also repeating the experiment enables mean to see anomalous results clearly My control variables are; the size of the potato, the temperature of the solutions, the volume of the outside solutions and the length of time the potato cylinders are left in the solutions. Independent Variable;

My independent variable is the concentration of the solution.

Dependent Variables;

My dependent variables are the volume of the potato cylinders and the mass of the potato cylinders.

Apparatus

Clock

Knife

Balance

Test tubes

Test tube rack

5cm3 Syringes

Beakers

Tissue paper

Weighing scales

Distilled water

Sucrose

 

Fair Test

        

        I will make sure this experiment is fair because if the experiment is not carried out fairy the results I am obtaining maybe wrong, and this will lead to a wrong conclusion. I will make sure that the potatoes are weighed correctly before they are placed in the solution. I will also make sure that the potato are fully covered by the solution, this is because the potato should have total contact with the solution. I will also make sure that any skin on the potato is peeled of because the skin may affect the osmosis taking place. I will also make sure I time all the potatoes correctly and make sure they all have an equal amount of time in the solution. After conducting the experiment I should make sure I dry each piece thoroughly this is to prevent any solution not absorbed by the potato being weighed will also use different syringes for the sucrose and water solutions this is to stop the solution the measurement of the solution being inaccurate. I will also perform each experiment at room temperature because I know that temperature affects osmosis. I feel if I carry all these task out I will have obtained reliable results.

Safety

Safety is important in any experiment and even though I am not using, irritant or corrosive solutions there is still a chance of sustaining an injury. However there are few dangers that could incur while conducting this experiment. I am using a sharp knife while cutting the potato and I could harm myself or somebody else if it is not handled probably.

Results

        After the experiment I dried the potato pieces on tissue paper this was to prevent any water outside the tissue of the potato affecting the weight.

        

Experiment 1

Experiment 2

Average loss/gain weight of Potatoes

 Analysis 

         I feel the results I obtained are reasonably accurate has I tried to make the test as fair as possible. Using my graph I am able to see as the strength of the solution decreases the potato weight increases.  My graph shows this by the line sloping downwards as the strength of the solution increases. The weight of the potato increases as the solution becomes weaker. This is because the water molecules from a weak solution which is the concentration of 0.0 molar to a strong solution which is the potato.

Evaluation

         I followed my plan correctly and managed to gain accurate and sufficient results. I also managed to prove that my hypothesis was correct.

However to make my result more accurate I could have carried out one experiment at a time decreasing the time it takes to get the potato chip onto the weighing scales. This would increase the chance of getting an accurate reading. Using more types of molar solution would have also made the results more accurate and better results; doing this I could have made sure all my results were totally correct. Also maybe leaving each set for an hour this would have enabled Osmosis to reaches full capability, therefore telling me how much water could be transferred from each solution. However I did not have enough time to carry out each set for an hour. Also maybe repeating the experiment four times would have given me more accurate results and also showed up any anomalous results. Because I only carried out the experiment twice no anomalous results were clearly visible. Therefore I have no anomalous results. I could have also used more accurate syringes to make sure that the measurements of each solution were accurate, therefore producing more reliable results.

        Overall I am pleased with my experiment given the time I had to carry out the experiment and also the apparatus available to me, I was able to obtain reliable.