Practical Investigation On Osmosis Biology Essay

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In this investigation I am going to investigate the topic of Osmosis. I will be doing this investigation to find out whether I can prove the theory of osmosis The movement of water from a less concentrated solution to a more concentrated solution through a partially permeable membrane [1] or not by my simple experiment on potato chips.

The aim/ purpose of the investigation are to investigate the effect of sucrose concentration on osmosis in potato tissue, to find out how the concentration of sucrose solution affects the mass of potato and also to find the isotonic point of potato.

Osmosis is the movement of water molecules, across a partially permeable

membrane, from a region of high concentration of water to a low concentration of water molecules.

http://deltabiology.com/wp-content/uploads/2012/01/osmosis3.gif

Isotonic solution is the solutions being compared have equal concentration of solutes. [2]

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Hypertonic solution is the solution with the higher concentration of solutes.[2]

Hypotonic solution is the solution with the lower concentration of solutes. [2]

http://library.thinkquest.org/C006669/media/Biol/img/solutions.gif

Turgid cell is a cell which contains a lot of intracellular fluid and is swollen. [3]

Flaccid cell is the lost of water or not enough water is available for cell and the cell becomes weak, lax and soft. [3]

http://t0.gstatic.com/images?q=tbn:ANd9GcRhBnvBrK4FWGg7j2agIpG4-10RUJldJwtjtwXM7Jm1w6bf4Vut&t=1

Equipments

To do this investigation I have used different equipment such as potato chips, distilled water, sucrose solution, scalpel, chopping tile, ruler, measuring cylinder, test tube, tube rack, digital scales, filter paper, labels and Petri dish.

I have used potato chips, distilled water and sucrose solution to check the rate of osmosis in potato chips when distilled water and different concentration of sucrose solution is added.

I have used scalpel to cut the potatoes in the size I need and also used to make the surface equal of all the potato chips.

I have used the chopping tile to place the potato while cutting. I have used chopping tile because it doesn't let the scalpel to cut the table and also it reduces the hazard.

I have used a ruler to measure the length of the potato to make the same size. I have used the ruler which gives the measuring nearest to (+/- 1mm).

I have used measuring cylinder to measure the amount of distilled water and sucrose solution. I have used measuring cylinder because it is measured in cubic centimetre (cm3) nearest to 1cm3, which will help to make the investigation more precise.

I have used test tubes in the experiment to store the different concentration of sucrose solution.

I have used test tube rack to hold the test tube containing the solution. I have used test tube rack because it holds test tube from top to bottom and has flat surface which reduces the chance of spilt of solution.

I have used digital scale to measure the mass of the potato before and after. I have used digital scale because it gives the measurement in 0.01g which makes the result very precise and it also give exact result where as normal weighing scale might have different result because the direction you look at the scale makes the difference.

I have used filter paper to remove the extra excess liquid from the potato chips before and after the experiment. This is because it will give more accurate result.

I have used Petri dish to put 3 potato chips in one sample so that we can get average result which will be more reliable.

I have used the labels to label the Petri dish and make sure that the Petri dishes do not get mixed up which prevents incorrect result due to this factor.

Safety

Wear hand gloves while using solutions as it can cause skin irritant due to a risk of having allergies or sensitive skin.

Long hairs should be tied and any long jewellery should be taken off as it might get tangled while working and might get stuck in places and might lead to serious hazard.

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Do not run while carrying equipment as it can fall and cause serious accident example broken glasses can cut you or other people.

Be very careful while chopping the potatoes because the scalpel we use to the potatoes is very sharp so we must make sure that we don't cut our fingers.

Make sure you don't pour water everywhere during the experiment because it makes the floor wet and slippery and someone might be slipped.

Put the scalpel in the correct place after chopping the potatoes because it is misplaced then it might cut someone else while searching other things.

Hypothesis

The mass of the potato will decrease as the concentration of sucrose solution increases. This is because I have researched in osmosis and isotonic, hypertonic and hypotonic solution, turgid cell and flaccid cell. And the information I have found direct me to come up with this hypothesis. This is why I predict that potato chips placed in distilled water will undergo and gain in weight and potato placed in sucrose solution will lose weight. I have made this prediction based on scientific knowledge of the special type of diffusion known as osmosis.

Preliminary Test

Firstly I did my preliminary test before my main investigation to make sure that my investigation will be accurate and reliable. And also to check if the investigation I am doing works.

Method

First of all I collected all the equipment that is needed for the investigation.

As the surface area of the potato chips varied, therefore I chopped potato chips using scalpel on the chopping tile with same size to make the length and surface area same as possible.

As the potato chips were put in the isotonic solution I removed the extra excess liquid from each of the potato chip with the filter paper.

Then I measured the mass of every potato chip using digital scales and recorded the mass in my table.

I labelled the Petri dish with numbers from 1 - 5, to put the different concentration of sucrose solution and potato chips into it.

The total amount of solution in my test tube is 50 cubic centimetre (cm3) so I put different concentration of sucrose solution in Petri dish using measuring cylinder.

Then I put 1 potato chip in each Petri dish and left it for 15 minutes.

Potato chips

5

Sucrose solution

Distilled water

6

4

1

3

2 C:\Users\Kiran\Documents\kiran\Biology\Untitled.jpg

Result table

Concentration of sucrose solution(mol)

Mass before

(g)

Mass after

(g)

Changes in percentage (%)

0.00

0.25

0.50

0.75

1.00

Preliminary test graph analysis

These are the result for my preliminary test. In my preliminary test I have measured the mass of potatoes before dipping it into the sucrose solution and after dipping it into sucrose solution and after. I collected this data and calculated it to find the changes in percentage (%).

The problems occurred and solution during preliminary test.

During my preliminary test crisis occurred in between which are as follows:

Factors

Effect

Control

Different changes

The difference in temperature affects the reaction time in different potato chips. This will cause the result to be inaccurate.

To control this factor I kept the entire sample in same temperature (room temperature).

The remaining of excess liquid in potato.

The remaining of excess liquid in potato will affect the mass of potato and the results we get won't be accurate.

To control it I used more and more filter paper to absorb all the excess liquid until the potato chip is dry. I did this before the potato chip is dipped into the solution and after potato chip is dipped into the solution.

Using big potato chip.

Using big potato chip didn't fit in the Petri dish and it causes the solution to expel from the Petri dish which caused the floor to be wet.

To control it I used scalpel to cut potato chips into small length so that it can fit into Petri dish easily.

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Remains of sucrose solution in measuring cylinder

The remains of sucrose solution in measuring cylinder will result the Petri dish with different molarities.

To control it I washed the measuring cylinder each time it's being used so that the measuring cylinder we use won't be contaminated with sucrose solution and also there will not be any error on the mass of the potato.

Summary of preliminary investigation

First I did the preliminary test before starting to do my main test. In my preliminary test I tested potatoes in 5 different samples where concentration of sucrose was from 0.00 mol to 1.00 mol of 20ml. In my preliminary test I used just 1 potato chips in each concentration to check if the osmosis takes place but I couldn't find out if the investigation was reliable and accurate or not because I didn't have any average result or range of results, thus I have used 3 potato chips in each concentration for my main test so that I can find out the average result which makes my investigation more reliable. The potatoes were stored in the isotonic solution where the concentration of solution and water was same. But the rank of water in isotonic solution was different to the rank of water inside the potato which gave us the fault result so in my main test I made sure that the isotonic solution was correct so the result I get will be accurate. In my preliminary test I left my potatoes with different concentration for fifteen where there was different temperature in the room because some concentration was placed near window and some were placed far away from the window, therefore in my real investigation I left my potatoes for 15 minutes all in same place where temperature won't affect the result. In my preliminary test I did not wash measuring cylinder each time after I use it, which resulted the test tube with different molarities, therefore I washed the measuring cylinder each time I use it in my main test. From my preliminary test I got positive idea of isotonic solution and length and surface area of potato chip which lead to make my main investigation as accurate and reliable as possible.

Main test

Method

First of all I collected all the equipment that is needed for the investigation.

As the surface area of the potato chips varied, therefore I chopped potato chips using scalpel on the chopping tile with same size to make the length and surface area same as probable.

As the potato chips were stored in the isotonic solution I removed the extra excess liquid from each of the potato chip with the filter paper.

Then I measured the mass of every potato chip using digital scales and recorded the mass in my table.

I labelled the Petri dish with numbers from 1 - 6, to put the different concentration of sucrose solution and potato chips into it.

The total amount of solution in my test tube is 50 cubic centimetre (cm3) so I put different concentration of sucrose solution in Petri dish using measuring cylinder.

Then I put 3 potato chips in each Petri dish and left it for 15 minutes.

After 15 min I took out the potato chips from the solution and with the filter paper I removed the extra excess liquid from each of the potato chip as I did before.

Then I put the potato chip in the digital scale and recorded the result in result table.

6

Potato chips

Sucrose solution

Potato chipsDiagram

6

2

1

Sucrose solution

5

4

3

Distilled water C:\Users\Kiran\Documents\kiran\Biology\Untitled.jpg

Result table

Petri dish with concentration

Potato chips

Mass before

Mass after

Difference in mass (%)

[1] 0mol

1

2.05

2.08

1.46

2

2.12

2.14

0.94

3

2.09

2.13

1.91

[2] 1mol

1

2.08

2.07

-0.48

2

2.24

2.27

1.34

3

2.20

2.22

0.90

[3] 2mol

1

2.09

2.10

0.48

2

2.07

2.09

0.97

3

2.02

2.04

0.99

[4] 3mol

1

1.93

1.91

-1.04

2

1.94

1.93

-0.51

3

1.93

1.90

-1.55

[5] 4mol

1

1.62

1.57

-3.09

2

1.57

1.55

-1.27

3

1.41

1.39

-1.42

[6] 5mol

1

1.66

1.62

-2.41

2

1.52

1.48

-2.63

3

1.74

1.68

-3.44

Average result

Petri dish with concentration

Average mass before

Average mass after

Difference in mass (%)

[1] 0mol

2.09

2.12

1.43%

[2] 1mol

2.17

2.18

0.46%

[3] 2mol

2.06

2.08

0.97%

[4] 3mol

1.93

1.92

-0.51%

[5] 4mol

1.53

1.50

-1.96%

[6] 5mol

1.64

1.59

-3.04%

Main test graph analysis

These are the result of my main test. After my main test I found out the average result of my test which I used to plot my graph. There are also some outliers in my set of results. In Petri dish2, chips1 which is highlighted green is an outlier because the mass of the potato should be increasing instead of decreasing. There is also an outlier in Petri dish 5, potato 1 which is highlighted yellow because the mass of the potato should be decreasing like in other samples rather than decreasing too much shows a big difference in the percentage change. Therefore it is a common outlier.

Analysing graph using scientific background

Evaluation

I believe I have gained enough results as shown on the graph and the tables that concludes the experiment, and to prove my hypothesis. I have obtained a good amount of fairly accurate results from which I was able to draw informative and reliable graphs. I believe I took enough repeat results for the number of concentrations I was using also the time I used was sufficient to prove that osmosis had occurred. My final results were very reliable, due to the precautions I took to make this a fair test.

However there were some anomalous results. I believe these were caused by some of the reasons highlighted below and also the fact that I could not control any temperature variations of the liquid within room. I could have controlled this by placing the beakers in a water bath kept at a constant temperature and by covering the beaker in cling film to prevent moisture escaping.

Even though there were anomalous results, and that I would have to repeat those results more to prove completely conclusively that the graph is completely correct, there is definitely a negative downward trend across the graph, proving my conclusion correct.

I believe that my procedure was suitable for my experiment and I would improve it with the previous factors mentioned above and the list of factors mentioned below. I believe that overall my results were fairly accurate, and a firm conclusion can be drawn from them. Looking at the overall experiment, I have thought of a number of things that would have helped to make the experiment more accurate. The potato cores all had different levels of moisture at the start of the experiment, meaning that some potato cores would need less osmosis to reach equilibrium within the same morality solution.

The concentrations were measured out using a measuring cylinder, which was not completely accurate. The experiment would have been far more exact if there had been some form of exact measuring device, perhaps digital.

The experiment would have been more exact if I had found a way of removing and measuring all the sores at the same time to reduce the time difference between weights being measured.

I did try to keep the cells the same, but this was very difficult, as I had no way of telling their exact age. I also tried to use the cells from the same potato; however the potato didn't have enough cells to cut enough cores from for all the results and therefore I was forced to use two different potatoes.

The scales I was using gradually became sticky due to all the potato cores, therefore more weight may have been added later because of the excess water and sugar.

Conclusion

Therefore I can conclude that my investigation was reliable and accurate because it supported the theory of osmosis and showed that isotonic point of potato chips I used in my potato was around 0.29M which falls under the range that isotonic point of the potato chip is between 0.2M - 0.3M. This concludes that my investigation was accurate and reliable. In conclusion, I can say that the movement of water through a semi-permeable membrane (the process of osmosis) is affected by the concentration of sucrose solution, or by any other solution. The higher the concentration of glucose solution, the more the potato chip will lose its mass. All the evidence I have obtained supports my hypothesis. I have been able to collect sufficient results by doing the experiment with three different potato chips in other word repeating my experiment three times.

However there are improvements that could be made which are given in evaluation. Because water molecules have a form of kinetic energy, they are always moving around in either a gaseous, solid or liquid state, randomly from one place to another. The greater the concentration of water molecules in a solution, the greater the total kinetic energy, and higher the water potential will be. This means that as the concentration of sucrose molecules increases in a solution; the concentration of water decreases also the water potential resulting in decreasing of a solution's ability to move between solutions due to osmosis.

Therefore as the concentration of sucrose increases in each solution, the water in that solution is less able to move to the potato, causing water from the potato to move into the solution, decreasing the potato's mass. An osmotic system is set up when a semi-permeable membrane is placed between two solutions. There are many examples in the biological world, in many plants and animals. A semi-permeable membrane occurs when some substances with small molecules can pass through, e.g. Water, and some substances cannot pass through the membrane because they have larger molecules, e.g. Sucrose. The permeability of a membrane varies with certain conditions, and can vary due to temperature. My investigation shows that there is no prevent in water loss, suggesting that the cell is not completely plasmolysed. However, it is important to realise that this is only an estimate because potato cells are not uniform in their concentrations.