For my results, I will take the mass before and after of all vegetables, twice due to repetition of the experiment. I will then calculate the mass change in both experiments for all vegetables, and find the average. I will also obtain % change and place this in a bar chart.
I researched the sugar content of my selected vegetables using the Internet, and I found that:
- Parsnip-9mg/100g
- Potato- 7.7mg/100g
- Swede-7.2mg/100g
- Sweet Potato-7.7mg/100mg
- Carrot- 6.8mg/100g
When I have the results, these figures should allow me to prove and support my conclusions, or show the lack of accuracy and fault in my experiment.
Results table for mass change:
Results table for percentage change:
- I will put the results into bar and/or pie charts in my analysis.
I know that osmosis will occur in the vegetables, but I am not sure of the exact amount that will take place. There will be a 0.2M solution on the outside of the vegetables and depending upon the amount of sugar and water in the vegetable, the solution will transfer into the vegetable and it will make an even balance of sucrose solution in both.
Last year I did an osmosis experiment which used different sucrose solution concentrations as the variable. This showed that the greater the concentration, the less percentage change and mass change, occurred in Potatoes alone. This was because osmosis is water moving through partially permeable membranes, and the more sucrose in the solution, the less water will diffuse and less % change will occur.
The past experiment inspired me to do an osmosis experiment, but with completely different variables. It also gave me an idea of how osmosis works and which variables work and shouldn’t be altered.
I used my 4th form exercise book with notes on osmosis for reference, as well as ‘Letts guides’ and ‘CGP GCSE help books’ to gain knowledge about osmosis. I used ‘http://www.galactosemia.org/vegetable.html’ to obtain the sugar content of the vegetables.
Simple diagram of how osmosis moves small particles from cell to the surrounding area.
Skill O- Obtaining
I used all of the equipment on my apparatus list in the planning section. I also adhere to my safety procedures and the experiment was carried out successfully.
I have a sufficient amount of results, as I did the experiment twice. This was averaged out to make percentage change and mass change results. This is more than one set of results so it will give more reliable evidence, and allow me to make a better evaluation of the experiment.
Results table for mass change:
Results table for percentage change:
My results are accurate as I used sensitive scales to weigh the chips, so they gave me an extremely exact figure. They also gave me the mass gained per hour on average from the repeat readings. These are very small amounts but are still relevant. The amount changed per hour is the rate, mass gained by the different vegetables in one hour.
I cut the chips to 5 x 1cm and placed them in 10ml of 0.2M sucrose solution. I did two identical experiments at the same time. I weighed the chips before and after I had left them for one hour. Using the sensitive scale I recorded my results, and then found the percentage change.
Skill A-Analysing
I have found that Parsnip has the fastest rate of osmosis, and has the largest percentage change. This is in my opinion the sweetest tasting vegetable of the group as well. The order for largest amount of osmosis that took place in the hour is:
-
Parsnip (1st)
- Potato
- Swede
- Sweet Potato
-
Carrot (5th)
The results are very small in difference, which were recorded in one hour. They change mass by under 0.5g each so this makes it harder to make an evaluation successfully. The percentage changes were small, but also similar to one another.
Results:
This shows the percentage changes when experiment one and two were averaged. This means the results will be more accurate.
Pie chart to show average mass change (g):
Using the chart and graph above I can see that Parsnip is clearly the vegetable which has the fastest rate of osmosis, and is affected the most by the experiment. We can prove the earlier stated order of vegetables, and partly my original theory that the sweeter tasting vegetables will gain the most water.
Through my research on the Internet I have found that the sugar content of the vegetables is:
- Parsnip-9mg/100g
- Potato- 7.7mg/100g
- Sweet Potato-7.2mg/100g
- Swede-7.7mg/100mg
- Carrot- 6.8mg/100g
This coincides partly with my results.
Parsnip has the highest sugar content and is also the most changed by osmosis in my experiment. Potato is second in both lists as well. In the sugar list, Sweet Potato is followed by Swede and then Carrot, but in my list Swede gains more water than Sweet Potato.
I can conclude that the vegetables with higher concentrations of sugar in them will gain more water and grow in size and mass. This is because the rules of osmosis apply. When the cell has high sugar and low water amounts and is placed in a surrounding with more water, balance is necessary, which is why the water moves into the cell at a higher rate. This would explain my results with the exception of the anomalous results.
My prediction was roughly correct. With quantities as small as these it is hard to be precise and one has to allow a decline in accuracy.
Skill E-Evaluating
The experiment worked relatively well, and did go to plan except for a few minor problems. The small difference in the results was one of the main problems along with the accuracy. Being a GCSE student in a school laboratory is not the most professional environment to carry out an experiment if one wishes to obtain perfect results. Due to the results not being drastically changed from the beginning masses, mistakes were allowed, and it was harder to see the clear differences in vegetable results. Despite this the experiment worked well and gave me an idea of the effect of osmosis on different vegetables.
I think I had enough accurate results, but the problem was the timing of the experiment. The chips stayed in the solution for one hour. Had this been longer, the results would have separated from each other and may have given a more clear overall result.
If I were to re-do the experiment, I would leave the chips in the solution for a longer time, or possibly see what the results were at different intervals. I might have also changed the sucrose solution to a higher or lower concentration.
I recorded the order of mass and percentage of the vegetables to be:
-
Parsnip (1st)
- Potato
- Swede
- Sweet Potato
-
Carrot (5th)
But my research showed that I had Swede and Sweet Potato in the wrong order. This anomaly is disregarded because the results were so close together that it would have been possible for the scales to pick up excess wind or someone may have lent on the table at the same time, (Swede-0.25g, Sweet Potato-0.235g). The results were within 0.015g of each other. This would explain the anomaly.
When I repeated the experiment the results varied from the previous experiment. This shows that it was extremely easy to make mistakes in the experiment, and that I may not have cut the chips to an exactly identical size. This just proves that the data was unreliable, but still gave an idea of the experiment, and what the results should have been.
To improve the method, I would have used a machine to cut the chips to an exact size, along with making sure that all the measurements were correct and accurate. I would also leave the chips in the solution for a longer time, as to obtain better results. This would also reduce risk of errors and anomalies.
To extend my work I can do other experiments of a similar nature. For example I could vary the sizes of the chips to see if that affected the results, and also change other variables, which I kept constant in this experiment.
April 2004
