Investigation to find out the affects of osmosis in a potato.

Investigation to find out the affects of osmosis in a potato

Aim: We are going to find out the affect of osmosis in a potato. Looking to see where the concentration changes and where water is lost or absorbed. Also we will investigate how the mass and length changes.

Prediction: I already know from my research that osmosis is,

“The movement of liquid from a high concentration, to where there is a low concentration, through a semi-permeable membrane”

With this knowledge I can predict that the higher the concentration of water in the cup, the more water will be absorbed by the potato. Therefore the mass of the potato will increase. When the concentration of water in the cup decreases, the amount of water being absorbed will become less. This will continue to a certain point when the concentration of the potato is greater than the water, and the potato will release water.

After looking at results from a previous experiment I can say that when the concentration was over 7%, the potato absorbed water and it grew. This backs up my prediction. Eventually the cells of the potato cells will become turgid and will not be able to take on any more liquid as they are full.

The lower the concentration, the less water is absorbed. When the concentration is lower than around 10%, water is released from the potato. The reason the potato releases water is to create equilibrium (Equal concentration inside and outside of the potato).

Equipment:

The reason for using distilled water is that we know it is 0% concentrate. This makes it much easier to work out the concentration when salt is added, but it also helps keep it a fair test. Using a cork borer is good as the diameter of the potato chips will be almost exactly the same on every chip.

Method: Firstly we will put equal amounts of water into the six cups. We will use 100ml of distilled water in each cup; using a total of 600ml. Using an equal amount in each cup helps to keep ...

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Equipment:

Method: Firstly we will put equal amounts of water into the six cups. We will use 100ml of distilled water in each cup; using a total of 600ml. Using an equal amount in each cup helps to keep it a fair test. Using 100ml is also good as this tells us that, 1ml = 1%. Then using the cork borer we will cut out 6 pieces of potato at approximately the same size. Our chips turned out at,

Length = 4.5Cm and the diameter = 1cm.

We then measured and weighted the potato chips, recorded these measurements and added one chip to each pot.

Diagram:

We left this overnight to allow time for any changes to happen. We left them on a window sill, covering the top with cling film. We covered the top with cling film to keep it a fair test. Using cling film made it so that nothing could get in to affect the solution, but also so that no water would evaporate.

Preliminary Results:

The table below shows the before and after weights and masses of three potato chips, we chose to do three as it is a good number to show a short trend.

Going up in groups of 5% is a big enough range to give us a wide variety of data. But it is also small enough to keep the data relevant to the experiment. I can already see a result which I think is wrong, but when I have completed a full test I can determine whether the result is wrong, or if my prediction is wrong.

Results:

I have highlighted any results which I think are incorrect. The reason for me highlighting them is that they do not follow my expected trend.

As I did not start off with the same length or mass for each chip, the data will be different. I can see that this has affected my results because a bigger chip of potato has more surface area in the water, meaning it is able to release or absorb more water than the smaller pieces. These results back up my thoughts in the preliminary tests that some of my results were wrong.

The graph below shows the differences between before and after mass of the potato chip.

I chose to link the points because it makes it clearer to see the relationship than if I was to use a line of best fit. 5%, 10%, 20%, 25% all follow the trend that I predicted. I think that my prediction was right, but 15% and 30% were anomalies.

I’ve drawn on a line of best fit to show where my results should have been.

Conclusion: After looking at my results in the table it is extremely hard to draw a conclusion. But when I looked at it in graph form, you can see that we made errors when conducting our experiment. 5%, 10%, 20% and 25% all follow the trend that I predicted, but 15% and 30% are wrong results. The line shows that the figures are not consistent. The reason why these results are out of place can be because of any of these things,

-Too much / too little water

-Too much / too little salt

-The potato chip was taken from a different potato, meaning it had a different concentration

-The container was not covered with cling film

-Measurements were taken wrong

By drawing on the line of best fit, it helps to show how my results should have been and from this I can see that my prediction was right.

Evaluation: I am disappointed that I could not make a unanimous conclusion but obviously our results were wrong. Even though the conclusion was not clear, I think that if we had taken a bit more time, we could have had better results. By drawing on a line of best fit I think it shows the trend and how our results should have been; but unfortunately they did not turn out this way.

I think that over all we carried out the experiment well, doing everything safely and keeping everything as a fair test. It is plain to see that at some points we made mistakes but overall I think we did well.

If I were to do the experiment again I would take more time setting up the experiment, making sure that every detail was right so that we would get the correct results.