Find out the effect of changing solute concentration on osmosis in potato tissue.

Temperature must be controlled at a certain level, I must not make it too hot which is above 40c otherwise the cells would stop working. I must insure that the cells are gaining enough energy from the heat and not make it too cold; the optimum temperature I thought was 37c. I will be controlling it by inserting the test tube including solute in the water bath.

Surface Area must be controlled by giving them all the same shapers and sizes. If we don't, then the one with more surface area will take more affect in osmosis. To keep the same diameter we will use the one borer on all of them, and then we'll use rulers to measure their lengths with. I think the best size to carry the investigation with is the size 6 borer, and it should be 3cm long.

Volume of the potato assured must be equal; different water potential of the potato may affect the outcome of our results. The way we can measure volume is after slicing the potatoes into shape. We can then use the Top pan balance to weigh them. If the surface area has been made reliable, it wouldn't matter if the volume is a little off because the difference in the change of volume will be recorded and it shouldn't affect the results as much - but try to keep as close as possible.

We must keep the Immersion Time the same. This way it will be reliable and will give all tests a fair amount of time. I think the best time I should use for this test is 30mins.

We have to see if the cells are alive, be analysing the colour to see if it looks healthy and not rotten. If it's dark and looks dead then we cannot use this potato chip to carry our investigation because osmosis might not take place. By cutting open with borer if anything looks dark, greyish or unhealthy then this potato chip can't be used.

We must use one Variety of Potato because using various potatoes will have different water potentials and will be grown in different ways. The way we can make sure this won't happen is by choosing one, and that one I choose to be is the Cultura variety.

The solution I chose for osmosis to happen in is sucrose. We will make different concentrations with this solute by mixing it with water.

Here are the mixtures:

Concentration (mole)

2.00

.75

.50

.25

.00

0.75

0.50

0.25

0.00

Water (ml)

0.00

0.25

0.50

0.75

.00

.25

.50

.75

2.00

Sucrose (ml)

2.00

.75

.50

.25

.00

0.75

0.50

0.25

0.00

Apparatus

Clamp stand (x2)

Burette holder (x2)

50ml burette (accuracy + or - 0.1ml) (x2)

00ml beaker

Funnel (x2)

Potato Borer (size 6)

Potato (cultural variety)

Scalpel

Ruler

White Tile

Test Tube Rack (x2)

Boiling tubes (x3)

Thermometer

Water Bath

Tissue

Top pan Balance

Stop watch

Sucrose (2 moles)

Distilled water

Wooden Stick

How to measure

In this experiment we will be measuring size of potato, concentration of sucrose solution, temperature, and time.

To control the size of the potato we will use borer size 6 and 3 cm long to all pieces of 9 potato chips. The reason why I chose to use 6 is because it's not too big and not too small.

We will use a 50ml Burette to measure the amount of water and sucrose we will add in our mixture of solutions. We will not use a measuring cylinder because it doesn't have a 0.1ml + or - measurement unlike the burettes.

I chose to measure 9 different concentrations because its not too little and 9 makes perfect for all the mixtures shown below:

Concentration (mole)

2.00

.75

.50

.25

.00

0.75

0.50

0.25

0.00

Water (ml)

0.00

0.25

0.50

0.75

.00

.25

.50

.75

2.00

Sucrose (ml)

2.00

.75

.50

.25

.00

0.75

0.50

0.25

0.00

To heat the test tubes and keep them constant at the optimal 37c, we will need to use a water bath

We will repeat the investigation 3 times for reliable results. And plot down all results on a table like the one shown on the next page. After doing all three we will use the average amongst the three. The average will lead us into finding the pattern of this investigation.

Concentration of sucrose Solution (m)

Mass of Potato Tissue (g)

Average Mass of potato tissue (g)

Difference in mass (g)

Trial 1

Trial 2

Trial 3

Before

After

Before

After

Before

After

Before

After

2.0

.75

.5

.25

.0

0.75

0.5

0.25

0.0

Procedure

. Set up apparatus like shown below

2. Fill one beaker with sucrose (2mole) solution

3. Fill the other beaker with distilled water

4. Pour the two beakers into separate burettes gently through the funnels without trapping any air

5. If too much water or sucrose is poured in- pour out slowly back into the beaker so that the number is on 0. It should be measured by the bottom of the meniscus

6. To get nine different concentrations of Sucrose - we will need to combine with distilled water but keep them all 20ml. You can mix sucrose and water by using one boiling tube and the amounts are shown below for which concentration you require. This table will show which mixtures would make which solution.

Concentration (mole)

2.00

.75

.50

.25

.00

0.75

0.50

0.25

0.00

Water (ml)

0.00

0.25

0.50

0.75

.00

.25

.50

.75

2.00

Sucrose (ml)

2.00

.75

.50

.25

.00

0.75

0.50

0.25

0.00

7. Pour concentration 2.0 into 3 boiling tubes for three different trials.

8. Leave on water bath and leave it to warm at the optimal temperature 37 c

9. Cut the potato with a Borer size 6 on a white tile and make three

0. Measure length of potato equally at 3cm then cut them using a scalpel

1. Weight them using a top pan balance

2. Plot the masses of all three potato ships on the table of results as 'before'

3. Get the stop watch ready

4. Put potato sips into the 2 mole sucrose solution.

5. Start Stop watch

6. Wait 30mins

7. Get out all potatoes with wooden stick

8. Use tissue to wipe excess solutions

9. Weigh them again using the top pan balance

20. Plot all three potato chips as 'after' on the table of results

21. Repeat the trial with different concentrations.

Results

Concentration of sucrose Solution (m)

Mass of Potato Tissue (g)

Average Mass of potato tissue (g)

Difference in mass (g)

Trial 1

Trial 2

Trial 3

Before

After

Before

After

Before

After

Before

After

2.00

2.05

.75

2.12

.84

2.05

.81

2.07

.80

-0.27

.75

2.04

.81

2.13

.92

2.04

.77

2.07

.83

-0.24

.50

2.06

.83

2.07

.86

2.07

.86

2.06

.85

-0.21

.25

2.05

.96

2.26

2.15

2.06

.91

2.12

2.00

-0.12

.00

2.06

.88

2.14

2.01

2.09

.87

2.09

.92

-0.17

0.75

2.06

.92

2.27

2.10

2.06

.92

2.13

.98

-0.15

0.50

2.06

.96

2.18

2.16

2.08

2.03

2.10

2.05

-0.05

0.25

2.06

2.06

2.19

2.21

2.13

2.23

2.12

2.16

-0.04

0.00

2.06

2.18

2.25

2.33

2.05

2.24

2.12

2.15

+0.03

Analysis

In this investigation I found out that the results where showing that as the concentration of the sucrose rose the lower the mass dropped of the potato chip. The line of best fit on the average difference in mass shown on graph indicates there has been a decrease of mass as the sucrose went more concentrated. The line drops down into a plateau.

For example my graph shows these results: It proves that the higher the concentration went the more water the potato chip lost.

2.0M > -0.27

.5M > -0.21

.0M > -0.17

0.0M > +0.03

These results came from osmosis. Osmosis is a special kind of diffusion it is the net movement of water molecules from a region of high water potential to a region of low water potential across a semi- permeable membrane.

This is a diagram showing where water from the dilute solute solution on the left passes through the semi- permeable membrane and moving into the high concentrated solute solution on the right.

If we add a potato tissue into a diluted solute solution, this makes the solute solution have a higher water potential compared to the potato tissue. Therefore the water from the surrounding solute solution will move into the potato chip to try and balance the water. This makes the potato chip to rise in mass by increase in water. When the cells have gained lot of water and they are strong, we call these cells turgid.

Therefore, if we add a potato tissue into a concentrated solute solution, this make the solute solution have a lower water potential compared to the potato tissue. And so the water from the potato will loose water to try and balance the scale. By losing the water it wall cause the mass to drop. When the cells have lost a lot of water and when they are weak we call the cells flaccid

I feel that my prediction was supported by my results. Because I predicted that as the concentration of the sucrose solution raised, the more water the potato chip will lose water. This also means that the less concentrated the sucrose is the more mass it will have.

Evaluation

I think my method was good because it supported my prediction. There was some room for improvements though. Because we found that some are anonymous results. We tried to figure why this might have happened.

I think using the burette was one of our most accurate and reliable piece of equipment. It can measure up to 0.1ml. There was nothing wrong with that.

Water bath can be put into 37c with no problems. It's reliable equipment. There's even a thermometer next to it so u can be extra accurate.

A borer was easy to use and reliable because of its cylinder shapes, can produce same shaped potato cuts each time keeping the surface area the same.

I used 9 different concentrations because it can used to make 9, easy to make, concentrations. Plus 9 concentrations are enough to make a reliable fair test.

We repeated the test three times because of reliability. One test is likely to make a mistake.

The reason why I think I got the anomalies is because, while putting them in and taking them out we had problems. Not enough people to plot them in at the same time however, I found out a way to solve this. This is how I thought it should be done. When plotting them in if we together had four hands we could have delayed the other lot about ten seconds then we get them out ten seconds earlier.