These results are based on the experiment in which the potatoes are cut into lengths of 6cm and are placed in 0% sugar, 10% sugar, 20% sugar, and 30% sugar water for 5 minutes.
It is clear that in the stronger sugar solution the potato slice increase more and that in the weaker concentrated solution it decreased. The reason being that the water in the potato is more concentrated than in the pure water, so the water diffused into the potato and therefore the opposite happens in the stronger solution as the water in the potato is less concentrated so water will need to diffuse out of the potato to even out the concentration of sugars in the liquid.
In the experiment I am conducting, I have decided that the dependant variable is the mass of potato because it is more accurate than the length as the potato could have expanded width ways as well as increased in length.
Variables:
Independent:
Concentration of sucrose solution- this is the factor I am testing therefore I have no need to control it.
Dependant:
The mass of the potato before and after osmosis- to see how much osmosis happened.
Controlled:
The type of potato tissue- a different type would maybe contain a different concentration of water in it therefore the results of the rate of osmosis wouldn’t be fair.
The type of salt- a different salt could have a different solubility therefore leading to unfair results.
The diameter of cork borer- a wider diameter means more surface area therefore it is more likely that osmosis will happen so the rate will be faster.
The volume of the solution- more volume of solution means more time for the process of osmosis to complete.
The temperature of water- a higher temperature will increase the energy in the solution therefore the particles will vibrate more so there is more chance of osmosis happening making it an unfair test.
Equipment:
Potato tissue- to be experimented on by placing in different concentrations of sugar solutions.
Cork borer 6mm- to take out the potato tissue from the potato more accurately.
Scalpel- to measure and put in the sugar solution.
Sugar- to be dissolved in water as part of the solution.
Water- in which the sugar will be dissolved in as part of the solution.
Ruler- to measure the length of the potato tissue.
Stopwatch- to measure the time in which the potato is allowed osmosis to happen when it is in the solution).
Beakers- to put the solution and potato pieces in.
Measuring cylinders- to measure the volume of water.
Method:
- Get all the equipment out.
- Use cork borer to get a potato cylinder, and then use the scalpel to cut it in to lengths of 6cm.
- Use distilled water in the first experiment.
- Measure the weight of the potato and record it.
- Insert the potato into the beaker with the pure water in it.
- Wait for 5 minutes then take it out and measure it.
- Repeat three times.
- Repeat the whole experiment but with 5%, 10%, 15%, 20%, 25% and 30% concentrated water with sugar.
- Record results in table and work out average.
Results:
I will use the standard error of the mean to work out inaccurate results. This method helps me to find out the percentage of difference the result has towards the average result. The result with more than 10% is an inaccurate result and will be highlighted in green. An anomalous result can be seen on a graph as a result that does no follow the pattern.
Line of best fit
Analysis:
From the graph it can see that as the percentage of sugar in the water gets higher the less mass increases. This is to do with the volume of water needed in the potato and the ratio of the water concentration inside and outside the potato. The potato piece with higher sugar concentrated solution (i.e. 30%) outside had a smaller increase in mass because; the solution outside the potato needed more water particles to reach equilibrium. Therefore less water could be diffused into the potato piece so there is less change in the mass than in a potato placed in a lower concentrated solution (i.e. 10%). This is as I predicted at the start of the investigation.
Evaluation
I think that the results I got were reliable because there were no anomalies. Using the standard error of the mean I found that there were only two inaccurate results which further supports the fact that the evidence are very reliable. If the were anomalous results they could have been caused by water loss in the tube or in the potato, therefore the concentration of water outside or inside would have change. Measuring mass instead of length is also better because the potato piece could have expanded width ways as well as length ways, also there could have been some air pockets in the potato which could have stored some water so not increasing the size at all.
To make my investigation better, I could have had a wider range of the variables, for example the sucrose solution could be up to saturation point. Doing this is can see when there is minimum amount of osmosis happening and even when osmosis is happening but the water is diffusing out into the sucrose solution instead of onto the potato.
