To investigate the effects of osmosis, in a potato, whilst in glucose and water.

Water molecules Sugar molecules

Method

* First of all we set up all of the apparatus.

* Once we had done that we poured the set amount of glucose and water in to the test tubes. In the first tube there was fifteen millimetres of glucose, in the second one there was ten mm of glucose and five mm of water, in the third tube there was seven and a half mm of both glucose and water, in the fourth tube there was 10mm water 5mm glucose in the fifth test tube there was 15 mm of water.

* Then we cut out five pieces of potato and then cut them down to three centre meters so as to make it fair. Then we placed them in to the test tube at one-minute intervals.

* After five minutes we removed the potato from the solution and measured its length and recorded them in a table.

Safety

It was not necessary to take any safety precautions, as there wasn't any thing dangerously in the experiment.

Fairness

So as to make this experiment fair we were very precise when measuring the amount of water and glucose. We also made sure that the five pieces of potato were the same length. As well as this we removed the pieces of potato exactly on time.

Variable used

The variable that we used was the amount of glucose and water that was used in each test tube.

Affecting variables

The possible variables were the:

Temperature,

Size of potato,

Length of Time which the potato, was left in the solution,

Amount of glucose and water in each test tube.

Measurement

We did two trials for the experiment and we did two ranges. The piece of potato was three centre metres each time and we used fifteen millilitres of solution.

Results

Time (minutes)

Test tube 1. (15mm glucose)

Test tube 2. (5mm water, 10 glucose)

Test tube 3. (7.5mm water, 7.5 glucose)

Test tube 4. (10mm water, 5mm glucose)

Test tube 5. (15mm water)

5

3.3

3.2

3.1

3.0

2.9

0

3.3

3.2

3.2

3.0

2.9

Time (minutes)

Test tube 1. (15mm glucose)

Test tube 2. (5mm water, 10 glucose)

Test tube 3. (7.5mm water, 7.5 glucose)

Test tube 4. (10mm water, 5mm glucose)

Test tube 5. (15mm water)

5

3.3

3.2

3.1

3.25

3.1

0

3.3

3.2

3.1

3.1

3.1

Time (minutes)

Test tube 1. (15mm glucose)

Test tube 2. (5mm water, 10 glucose)

Test tube 3. (7.5mm water, 7.5 glucose)

Test tube 4. (10mm water, 5mm glucose)

Test tube 5. (15mm water)

5

3.3

3.2

3.15

3.0

2.9

0

3.3

3.2

3.1

3.175

3.1

Analysis

From looking at our results I have observed that the potato expands more when it is placed in glucose. The potato floated more, at the beginning of the experiment, as osmosis had not yet occurred. As the experiment went on the potato began to sink further down in to the test tube due to the osmosis.

First set of results

Second set of results

Average set of results.

Average Results

Time (minutes)

Test tube 1. (15mm glucose)

Test tube 2. (5mm water, 10 glucose)

Test tube 3. (7.5mm water, 7.5 glucose)

Test tube 4. (10mm water, 5mm glucose)

Test tube 5. (15mm water)

5

3.3

3.2

3.15

3.0

2.9

0

3.3

3.2

3.1

3.175

3.1

My prediction is supported by the results as the slices of potato increased in size when they were placed in the mainly glucose solution more than when they were placed in the mainly water solutions in fact the pieces of potato shrunk in the pure water. The glucose obviously induces osmosis whereas water doesn't.

Evaluation

This experiment is not particularly accurate as it was quite hard to remove the potato exactly on time therefore some samples spent more time in the solutions than others. This could well explain why there were so many anomalies. In order to improve this experiment I think that we would have to find an easier method for removing the pieces of potato, so that we could get them out on time.

There were anomalies in:

The first attempt, test tube 3 at ten minutes (3.2)

The second attempt, test tube 4 at five minutes (3.25)

The second attempt, test tube 5 at five minutes (3.1)

I think that if I were going to repeat this experiment then I would continue taking readings up to twenty minutes. As well as this I would run four experiments instead of only two.