Equipment for preliminary work:
- Potato
- Sucrose Solution - 10%, 20%, 30%, 40% and 50%
- Tile
- Cork Borer
- Scalpel
- Weighing machine
- Graduating pipette
- Test tube rack
- Ruler
- Boiling tubes
- Labels
- Water
Method for preliminary work:
1. Get a few potatoes and a cork borer, when you have both of them take out as many potato chips as you can from one potato in total you should have 10 potato chips
2. When you have all 10 potato chips put them on a tile and use a ruler to measure the length and width and then cut them with a scalpel. (all potato chips should be 2cm)
3. When you have accurately cut them take all ten potato chips to a weighing machine to measure the mass. Record the mass for every potato chip in a table.
4. Once you have completed the table get 5 boiling tubes all the same size also get a graduating pipette. Use the graduating pipette to accurately measure the concentrations of sucrose solution, use 25 ml of each of the solutions-10%, 20%, 30%, 40% and 50%.
5. In each boiling tube put in two potato chips and then fill the boiling tube with the accurately measured sucrose solution at the same time.
6. Once you have all boiling tubes ready place them in a test tube rack and label each boiling tube with a sticker which says which % of sucrose solution it is.
7. When you have done all this leave the test tube rack for a day and after a day take them out and weigh them on the weighing machine again.
8. Again record all your ten results and then find two results where the mass of the potato chip increased as well as decreased. When you have found two different concentrations you will use those concentrations in your real experiment.
Preliminary table of results:
My results show that the mass of the potato increased and also decreased. They also show that as the sucrose concentration increased the mass of the potato chip decreased, this tells us that water was moving out of the potato and into the solution. This happened because the water always moves from a high concentration to a low concentration. This means that the potato chip was in a high concentration and the sucrose solution was in a low concentration.
Conclusion from Preliminary work:
I did the preliminary work to choose a more precise range of the concentration of sucrose solution. Now that I have carried out the preliminary work I am able to choose a more precise range I will be using a range between 0-20 %. I am choosing this range because my results show that between 0-20% of sucrose solution mass is gained and also lost .
After finishing my preliminary work I have chosen a range of the concentrations of sucrose solution which I will be using for my actual experiment. The concentrations of sucrose solution I will be using for my actual experiment are 8%, 10%, 12%, 14% and 16%.
Prediction:
I predict that when I will be using the following concentrations of sucrose solution 8%, 10%, 12%, 14% and 16% the mass of the potato chip will decrease as the concentration of the sucrose solution will increase. I can predict this from the results I got in my preliminary work. The potato would loose weight in a strong sugar solution and it would gain weight in pure water. Osmosis happens when water moves from a high concentration to a low concentration, so when a potato chip would be put in pure water it would gain weight because the water would be moving from a high concentration (pure water) to a low concentration (potato chip). However if a potato chip would be put into a strong sugar solution it would loose mass because the water would be moving from a high concentration (potato chip) to a low concentration (strong sugar solution). I also predict that the concentration of sucrose solution at 8% and 10% the potato chip will gain mass and the rest, 12%, 14% and 16% of sucrose solution will make the potato chip loose weight. The evidence I have is that in my preliminary results the solutions at 10% or less did not make the potato chip loose weight. Taking the results I got from my preliminary work the type of graph I will be expecting will look something like this:
Fair Test:
My input variable will be the sucrose concentrations of 8%,10%,12%, 14% and 16%. I will see at which sucrose concentration the mass of the potato changes, either less mass or more mass.
Output variables:
- Keep the amount of sucrose solution the same by measuring 25ml accurately with a graduating pipette, if not measured accurately the results will not be reliable.
- Make sure you have the same size potatoes, measure the width and length with a ruler so it is 2 cm. If not kept at same length and width the potato chip will have different amounts of cell sap, which can lead to unreliable results.
- The amount of time the potatoes will be kept in the sucrose solution needs to be kept the same
- The temperature also needs to be kept the same be cause at different temperatures the rate of osmosis may increase or decrease.
Safety:
In an experiment like this there are strict rules on safety.
- Do not drink or mess about with the sucrose concentrations.
- Use the cork borer on a potato which is placed on a table.
- Do not throw around any potatoes.
- Be careful with the scalpel, do not run around with it.
Equipment:
- Potato
- Sucrose Solution - 8%, 10%, 12%, 14% and 16%
- Tile
- Cork Borer
- Scalpel
- Weighing machine
- Graduating pipette
- Test tube rack
- Ruler
- Boiling tubes
- Labels
- Water
Method:
1. Get a few potatoes and a cork borer, when you have both of them take out as many potato chips as you can from one potato in total you should have 10 potato chips
2. When you have all 10 potato chips put them on a tile and use a ruler to measure the length and width and then cut them with a scalpel. (all potato chips should be 2cm)
3. When you have accurately cut them take all ten potato chips to a weighing machine to measure the mass. Record the mass for every potato chip in a table.
4. Once you have completed the table get 5 boiling tubes all the same size also get a graduating pipette. Use the graduating pipette to accurately measure the concentrations of sucrose solution, use 25 ml of each of the solutions-8%, 10%, 12%, 14% and 16%.
5. In each boiling tube put in two potato chips and then fill the boiling tube with the accurately measured sucrose solution at the same time.
6. Once you have all boiling tubes ready place them in a test tube rack and label each boiling tube with a sticker which says which % of sucrose solution it is.
7. When you have done all this leave the test tube rack for two hours and after a day take them out and weigh them on the weighing machine again.
8. Record those results in a table and use those results to draw a graph.
Results Table:
Analysis:
All potato chips increased or decreased in mass. At 8% both potato chips that were put into the sucrose solution have gained mass by 0.2g. At 10% both potato chips have also gained mass by 0.1g. However at 12% both potato chips have lost mass by 0.1g. But at 14% one potato chip lost mass by 0.2g and the second potato chip lost mass by 0.1g. Than at 16%b both potato chips lost mass by 0.2g.
The different masses of the potato chips show us that the concentration of the sucrose solution may not have been the same, because the osmotic potential could have been either higher or lower in the potato chip than the solution outside.
At 8% and 10% the potato chip may have been flaccid which allowed osmosis to occur, so the water moved from the sucrose solution (high concentration of water) into the potato chip (low concentration of water) which lead to the potato chip gaining mass. However at 12%, 14% and 16% the potato chip must have been turgid, which also allowed osmosis to occur, so the water moved from the potato chip (high concentration of water) to the sucrose solution (low concentration of water) which lead to the potato chip loosing mass.
Evaluation:
I think my experiment went very well, I started off with the right equipment and by making sure I keep everything the same so that I would not get any unreliable results at the end of the experiment. I started off straight away and followed the method I wrote down, by following the easy steps of my method I had the whole experiment ready to go in just a little time. I repeated the experiment two times to make sure that the results I would obtain at the end would be reliable. To make sure I had the right amount of everything I used a lot of equipment for example the graduating pipette, a ruler and a weighing machine. I measured and double checked everything and then proceeded with the experiment. Although I carried out my experiment very thoroughly I still received an anomalous result. At the 14% sucrose solution I put in two potato chips in the same concentration, however when I was collecting my results I noticed that although the mass of both potato chips were same at the beginning (2.2g) one of them had lost 0.2g and the other had lost 0.1g. This meant that something had gone wrong, maybe the temperature, the amount of time or the mass. So it was not a fair test as one result came out a bit wrong.
Next time to improve my coursework I will make sure I take all readings more accurately and also make sure that next time I will put all test tubes in an area where I’m sure the temperature will stay the same.
