Osmosis in Potato Tubes


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Osmosis in Potato Tubes

Osmosis:

Osmosis is the movement of water molecules through a semi-permeable
membrane from a high concentration to a low concentration.

Diagram:

[IMAGE]

[IMAGE]

Aim:

To see the effects of different concentration of sugar solution on
Osmosis in potato tubes.

Key factor:

In the investigation we change the sugar solution from:
0%-10%-20%-30%-40%-50% this is the independent variable; the dependant
variable is the change in mass.

Prediction:

I predict that all the potato tubes in pure water or low concentration
sugar solution will swell because water enters their cells by osmosis.
The potato tubes in higher concentration sugar solution will shrink
because water leaves their cells due to osmosis.

Equipment list:

* Cork borer

* Potato

* Sugar solutions – 0%, 10%, 20%, 30%, 40%, 50%.

* 6 Test tubes

* Test tube rack

* Scalpel

* Stopwatch

* Measuring cylinder

Fair test:

To make our experiment a fair test me need the same:

* Lengths of potatoes.

* Amount of sugar solution in each test tube.

* The potatoes have to have the same mass.

* Size of potatoes

* Diameter of each potato tube

* Time in sugar solution

We need to make sure in both experiments the fair test lists are used
and the procedures are carried out. This needs to be done otherwise my
results will not be accurate and will look odd.

Method:

Firstly we got out all our equipment. We then cut our potato tubes
with the cork borer and cut them with the scalpel so they were the
same length and weighed them. We then put one potato tube in each test
tube and then added the same amount sugar solution in to each tube.

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The concentration of sugar solutions varied in each test tube.

We then put the stopwatch on and left them for half an hour. After we
weighed each potato tube and recorded our results. We did the
experiment twice. We did this to make sure our results were correct.

Preliminary method:

We did everything the same as in our other experiment except we left
the potato tubes in the sugar solution for twenty minutes. We changed
the time we left the potato tubes in the test tubes to half an hour
because we didn’t see much change in twenty minutes.

Health and Safety:



The scalpel, which we used to cut the potato tubes, was very sharp.
The test tubes are made of glass so we had to be careful. Also we were
using a dirty potato and we had to cover up all our cuts so we didn’t
catch an infection.
======================================================================

Results Table:

Experiment 1:

Sugar Solution

Concentration

Mass of potato before (g)

Mass of potato after (g)

Change in mass (g)

Change in mass %

0%

1.253

1.223

+0.03

+2.3

10%

1.250

1.240

+0.01

+0.8

20%

1.283

1.253

-0.03

-2.3

30%

1.178

1.108

-0.07

-5.9

40%

1.173

1.083

-0.09

-7.6

50%

1.214

1.074

-0.014

-11.5

I did the experiment again to make sure my results were accurate.

Experiment 2:

Sugar Solution

Concentration

Mass of potato before (g)

Mass of potato after (g)

Change in mass (g)

Change in mass %

0%

1.533

1.483

+0.05

+3.3

10%

1.610

1.600

-0.01

-0.62

20%

1.558

1.528

-0.03

-1.93

30%

1.660

1.600

-0.06

-3.61

40%

1.605

1.545

-0.06

-3.73

50%

1.573

1.463

-0.11

-6.99

Graph: -

Conclusion:

I repeated the experiment to give me a more accurate set of results.
Also to see if my prediction was correct and it was because I said
that pure water or low concentration sugar solution the potato tubes
will swell and more water will enter their cells by osmosis. Also that
the potato tubes in higher concentration sugar solution will shrink
because water leaves their cells due to osmosis.

In my first results table I hade one anomalous set of results I have
highlighted it in red and have also circled in red on my graph. 32%
was a bit high and I would have expected it to be around 28% or 27%.
I’m not quite sure why this result was so high it may have been
because I weighed it incorrectly. In my second set of results I also
have an anomalous once again this is highlights and circled in my
graph. –2% is rather low and would of expected it to be around –5%.
This once again could be due to incorrect weighing.

In my second results table my results did what I wrote in my
prediction except from one of my results.

Evaluation:

In my experiment I think I had enough results. I also thought my first
experiment wasn’t accurate but my second experiment was. My results
are quite reliable but they could have been more reliable if I did the
experiment again. Repeating the experiment increases the reliability.

The reason I had anomalous results is because I obviously didn’t weigh
them correctly and if I did the experiment again I would weigh them
twice.

From my experiment I can conclude by saying potato tubes in low sugar
solution had a higher mass because there is more water entered by
osmosis. The potato tubes in high sugar solution will have a lower
mass because the water leaves by osmosis.

If I did the experiment again I would do it twice but at the same
time. So I can defiantly make sure that they are exactly the same.
Also I would make sure the potatoes are the same size and the same
make of potato.


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