Scientific Investigation about Osmosis
Scientific Investigation about Osmosis
Planning
As we know that plants take water from the soil to make food during photosynthesis. Photosynthesis occurs mostly in leaves. All plants have cells and all cells contain water and have a shape.
I am going to investigate, whether different concentrations of sugar solution effect the size and mass of the potato chips. In this investigation, I am using sugar solution and potato chips. When sugar is dissolved in water, it is known as sugar solution. This sugar solution has molarity, which is a measure of concentration. I am using different molarities of sugar solution to find the effect of concentration of sugar solution on size and mass of potato chips. Potatoes are made of plant's cells, because it is obtained from plants. By using potato chips, I will find the results about transfer of water in and out of plant cells. This in and out movement of water in the cells effects the size and mass of the cells in a plant. In this experiment the variables are 'Different concentrations of sugar solution'. Other factors that also effect the potato size and mass will remain the same. I will use same size and mass of potato chips and same volume of sugar solution in specific amount of time, but the concentrations of sugar solution will be different.
As we know that all plants contain a large vacuole. A vacuole is a fluid-filled space in the cytoplasm surrounded by a membrane. It is a permanent feature of the structure of the cell, with an important role to play. The vacuole of a plant cell is surrounded by a membrane called tonoplast. Vacuole is filled with cell sap, a solution of various substances in water. The water moves in and out, in the cells. This is due to Osmosis. Osmosis is the net movement of water molecules from a high concentration of water (dilute) or less concentrated solution to a low concentration of water (concentrated) or more concentrated solution across a semi-permeable membrane. There are three different types of solutions that are necessary to know in terms of osmosis, which are Hypotonic solution, Isotonic solution and Hypertonic solution. Hypotonic solution is a solution in which the osmotic concentration of solutes is lower than that in the cell. Isotonic solution is a solution in which the osmotic concentration of solutes is the same as that in the cell. Hypertonic solution is a solution in which the osmotic concentration of solutes is higher than that in the cell.
Prediction
I predict that the mass and size of the potato chip decreases, when the concentration of sugar solution is high. As simple, the lower the concentration or molarity of sugar solution the greater the mass and size of the potato chip. Because the higher the concentration or molarity of sugar solution the higher the particles of sugar present in the solution. As osmosis is the net movement of water molecules from an area of higher water potential to an area of lower water potential through a partially permeable membrane, therefore no sugar molecules can pass through the partially permeable membrane. This is because the partially permeable membrane allows the small solvent molecules of water to pass but prevents the movement of large solute molecules. Therefore the water molecules move out and the cell becomes flaccid. On the other hand, in the hypertonic solution there are less molecules of water and greater molecules of sugar solution. As in Osmosis, the net movement of water molecules from high concentration to low concentration across semi-permeable membrane, therefore, the water molecules inside cell will move out towards the sugar solution, which will decrease the size and mass of the cell. I predict that the higher the concentration of solute or lower concentration of solvent outside the cell, the smaller the mass and size of potato. Similarly, I predict that the lower the solute or higher the concentration of solvent outside the cell, the greater the size and mass of the potato. If the concentration of water inside and outside of the vacuole is same, then there will be decrease and increase in mass and size of potato chips.
Apparatus and Safety
The equipment that I am using in this experiment are Measuring Cylinders, Sugar Solution, Potato Chips obtained from Potato, Borer, Petri Dishes, Petri Dish Lid, Ruler, Stop Watch, Distilled Water, Filter Paper, Weighing Machine, Labels, Funnel, Knife, Body Protector and Eye Protector.
I should also make sure that I am wearing all protected equipment before starting experiment. As knife is dangerous, I should make sure that I use it safely and after use, I put it at safe place, so that, other students are protected from it. Borer can also be dangerous, because it has sharp end. While using Borer, I should make sure that I use it safely. I should use funnel, while pouring sugar solution in measuring cylinder to keep the surroundings clean and clear.
Method
First of all to test that the concentration of ...
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I should also make sure that I am wearing all protected equipment before starting experiment. As knife is dangerous, I should make sure that I use it safely and after use, I put it at safe place, so that, other students are protected from it. Borer can also be dangerous, because it has sharp end. While using Borer, I should make sure that I use it safely. I should use funnel, while pouring sugar solution in measuring cylinder to keep the surroundings clean and clear.
Method
First of all to test that the concentration of sugar solution effects the size and mass of potato chip, I took a potato. After that I bored in the potato with the Borer. I bored in the potato fifteen times and I got fifteen potato chips. Then I took the fifteen potato chips and cut them in length of 4-cm each without potato skin on the surface of the potato chip. All the potato chips had length of exact 4-cm. After that I weighed all the potato chips and recorded the masses. The range of their masses was between 2.8g and 3.3g. Then I took different concentrations of sugar solution. I took separately three times sugar solution of 20-centimetre cube in three separate measuring cylinders. I poured each 20-centimetres cube of sugar solution in separate Petri dish. The 20-centimetre cube of sugar solution had molarity 1. I labelled the Petri dish with the molarity of the sugar solution. Then I took separately three times sugar solution of 16-centimetre cube in three separate measuring cylinders and add 4-centimetres cube of water in each 16-centimetres cube of sugar solution. I poured each total 20-centimetre cube of sugar solution of molarity 0.8 in three separate Petri dishes. I labelled the Petri dishes with the molarity of the sugar solution. After that I took separately three times 12-centimetre cube of sugar solution in three separate measuring cylinders and add 8-centimetre cube of water in each 12-centimetre cube of sugar solution. I poured each total 20-centimetre cube of sugar solution of molarity 0.6 in separate three Petri dishes. I labelled the three Petri dishes with the molarity of sugar solution. After that I poured separately three times 10-centimetre cube of sugar solution in three separate measuring cylinders and add 10-centimetre cube of water in each measuring cylinder. I poured the three measuring cylinders containing 20-centimetre cube of sugar solution of molarity 0.5 in three separate Petri dishes. I labelled them with the molarity of the sugar solution. At last I poured separately three times 5-centimetre cube of sugar solution in three separate measuring cylinders and add three times 15-centimetre cube of water in each measuring cylinder. I poured the sugar solution of 20-centimetre cube of molarity 0.25 in three separate Petri Dishes. I labelled them with the sugar solution molarity. At last I put per potato chip in per Petri dish. I covered the top of the Petri dish with Petri dish lid and started the time. After 40 minutes, I took the potato chips and measured them with ruler. After measuring I covered the potato chip with filter paper, so that surface area containing extra water should be removed. I weighed them and recorded the results.
For fair test, I used exact length of potato chips. I used the sugar solution with correct quantity of 20-centimetre cube each time. I used the same surface area of potato chips and in same sizes of Petri dishes. For fair test, I used the potato chips without the skin on them. I used the same 40 minutes for every potato chip.
Analysing Evidence
With the help of experiment, I found that the length or size of potato chips decreases when the molarity or concentration of sugar solution is high. The experiment I did showed that when the molarity is 1, the length of the potato chips decreased to 2.7-cm, 3.3-cm and 3.3-cm from 4-cm of its original length. This showed that the average final length of potato chips decreased to 77.44% from 100% of its original length. My results showed that when the molarity is 0.8, the length of the potato chips decreased to 3.9-cm, 3.8-cm and 3.7-cm from 4-cm of its original length, which showed that the average final length of potato chips decreased to 95% from its original length of 100%.
The results that I got from the experiment shows, when the molarity of the sugar solution was 0.6, there was very little difference made to its original or initial length. The length of the potato chips decreased to 3.9-cm, 3.9-cm from its original length of 4-cm. One potato chip length increased to 4.1-cm from its original length of 4-cm, in the molarity of 0.6 of the sugar solution. This showed that the average final length of potato chips decreased to 99.17% from 100% of its original length. When the molarity of the sugar solution in the experiment was 0.5, the results that I obtained showed that the potato chips length increased instead of decreasing. The average final length of potato chips increased to 103.33% from 100% of its original length. This showed that the average final length increased 3.33% from its original length. As the molarity was decreasing the length of the potato chips was increasing. My results showed that the average final length of the potato chips increased to 105% from its original length of 100%. The increase in the length of potato chips was 5% from its original length of 4-cm.
On the other hand, the results of the experiment also showed that, when the molarity of the sugar solution was 1, the average final mass of the potato chips decreased to 77.44% from its original mass of 100%. Similarly when the molarity of sugar solution decreased to 0.8, the average final mass of the potato chips decreased to 86.36% from 100% of its original mass. As the molarity of the sugar solution decreased the mass of the potato chips increased. I got the result that, when the molarity of sugar solution decreased to 0.6, the average final mass of the potato chips decreased to 99.17% from its original mass of 100%. There was very little difference in the mass of the potato chips at molarity of 0.6 from its original mass. As the molarity of sugar solution decreased to 0.5, the average final mass of the potato chips increased to 110.69% from its original mass of 100%. Therefore, when the molarity of the sugar solution decreased to 0.25, the average final mass of the potato chips increased to 122.47% from 100% of its original mass.
My results showed that the length or size and mass of the potato chips increase, if the molarity or concentration of the sugar solution decreases. This increase in size or length and mass is due to Osmosis. Osmosis is when a hypertonic solution is separated from a hypotonic solution by a differentially permeable membrane, a net of flow of water molecules occurs through the membrane from the hypotonic to the hypertonic solution. When there is no longer a net flow of water both solutions are isotonic with each other.
This increase and decrease of size and mass of potato chips are due to hypotonic, hypertonic and isotonic. The presence of the cellulose cell wall makes a lot of difference too. Although it is freely permeable, it exerts an inward pressure on the cell and so has an effect on osmosis. If the cytoplasm of a plant cell contains more solutes than the surrounding fluids, water will enter the cell by osmosis. Similarly, if the vacuole contains less water molecules and more solute molecules than the surroundings, then the water will enter the vacuole by osmosis. The inward pressure of the cell wall builds up as vacuole swells and at this point cells are rigid, in a state known as turgor.
When the potato chips size or length and mass decreases water from the vacuole moves out by osmosis. When the water moves out, the size and mass of the potato decreases. In the experiment, from molarity of 1 to 0.6 of the sugar solution, the size and mass of potato chips decreases. This size and mass decreases because there are more sugar molecules outside of vacuole than inside, and there are less water molecules outside than inside. The water molecules have the only option to move in and out. This is because; the sugar molecules are too big to move in and out of selective permeable membrane. Only water molecules can move, because they are so small that they can move in and out of the selective permeable membrane. Thus the water molecules move out from the vacuole and when the water concentration inside and outside of the vacuole becomes equal, then water molecules do not move.
When the water molecules move out and very little water is remained inside, the cell becomes flaccid. When the cells shrivel and the concentrated cytoplasm loses its internal structure and ceases to function. This is called plasmolysis. When the water comes out in the Petri dish, the concentration becomes equal. Thus the cell loses its mass of water, which was present before, and size becomes small of less molecules of water, which was by water molecules.
Similarly, from molarity 0.5 to 0.25, the size and mass of the potato chip increases. This increases because the molarity of sugar solution is less. There are less molecules of sugar and more molecules of water in the sugar solution. Therefore, there are less molecules of water inside the vacuole than its surrounding. The concentration of water molecules is less than in Petri dish. The molecules of water in sugar solution will move in the vacuole, so that, the concentration of water inside and outside of the vacuole becomes equal. Therefore, the molecules of water in Petri dish will move inside and thus, the mass and size of the potato chips will increase. When the water moves inside the cell, vacuole push the cytoplasm towards cell wall, the cell is known to be turgid. Hence, the size and mass of potato chip increases, because water molecules' mass and occupied space, is added to the original size and mass.
As my predictions were that the higher the concentration of sugar solution or solute, the higher the decrease in size and mass of the potato chip. My predictions are 100% correct, as it is shown by the experiment. As I used the theory of osmosis in my prediction, therefore my prediction is correct. When a plant is put in a dilute solution, water tends to be transferred into the cell by osmosis. My prediction was correct, because osmosis is net movement of water molecules from high concentration to low concentration across a selectively permeable membrane. The water molecules will move from dilute hypotonic solution in the vacuole. This will result in increase in size and mass. In hypertonic solution the water molecules will move out of the vacuole. This will result in decrease in size and mass of the cell. Similarly, my predictions were correct and as in my prediction, in hypotonic solutions, the size and mass will increase. In hypertonic solutions the size and mass will decrease. But in Isotonic solutions there will be no effect on size and mass of the potato chips.
As we can see, in graph 1 that the length of potato chips increased or decreased when the molarity of the sugar solution is between 0.48 and 0.68. Therefore, at molarity 0.58, the potato chip size or length and mass will neither increase nor decrease. Similarly in graph 3, the mass of the potato chips increased or decreased between the molarity 0.52 and 0.69. Therefore, at molarity 0.6, the potato chips mass will not decrease or increase. The average molarity will be 0.59 (Shown in graph 5 also), where the size and mass of the potato chip will neither increase nor decrease.
When a cell is placed in a solution of lower water potential than it self, water leaves the cell exosmosis and the cell contents begin to shrink away from the cell wall incipient plasmolysis. At this point the cell is flaccid and no pressure is exerted by the protoplast against the cell wall. If water continues to leave the cell the plasma membrane is pulled away completely from the wall and the cell becomes plasmolysed.
If the cell is placed in a solution of higher water potential than itself, water enters the cell endosmosis. As the protoplast and vacuolar volume increases it exerts an increased pressure on the cell wall and prevents the elastic wall from contracting inwards. This is called turgor pressure and is equal and opposite to the wall pressure exerted on the protoplast. A cell in a state of turgor when it reaches its maximum turgor pressure.
These all effects are due to partially permeable membrane. A partially permeable membrane is useful for animal's cell and plant's cell. In plants, it also has very importance. Every cell has partially permeable membrane. It allows certain or special molecules to pass through. These special molecules can pass, because of their small sizes. Partially permeable membrane does not allow large molecules to pass in and out. As plants have cell membrane known as partially permeable membrane, it does not leave other unimportant substances to move inside cytoplasm. It is important, because it equals the water concentration inside and outside of vacuole, which effects the shape and size of the cell. Most of the chemical reactions occur in presence of water. To maintain this equilibrium, it works in a special way known as Osmosis. Other important substances such as chloroplast, mitochondria are stopped from moving outside of the cell. It does not allow important substances to move outside of the cell. It keeps the cell in shape in an important way known as osmosis. There is also membrane just inside the cell wall of a root cell, which is selectively permeable. The cytoplasm and cell sap of a root hair cell contain many solutes dissolved in water. Water found outside the cell, amongst the soil particles, contain solutes too, but at a much lower concentration. The root hair cell gains water from the soil by Osmosis.
Evaluation
In this investigation, as you know I did an experiment on potato chip about osmosis. I found some results that these potato chips increases or decreases in size and mass in different concentrations of sugar solution, as defined in analysing evidence.
My experiment was a fair test for a limit. It was a fair test for a limit, because I used exact the same length of potato chips. I used the same volume of sugar solution and I used the same surface area of potato chips and same sizes of Petri dishes, which gives the same level of sugar solution. In these Petri dishes, I used the same volume of sugar solution with different concentrations.
On the other hand, my experiment was not a fair test above the limit, because I used the same length of potato chip, but not the same mass. The masses of the potato chips were different. I used filter paper, so that it absorbs the solution on the surface of potato chip before weighing. It led to different absorption, which effected the masses of the potato chips. It was not a fair test, because I used one stopwatch for all potato chips. I put the first potato chip in the first Petri dish and when I put the last potato ship in the last Petri dish, I started the time. I also did not use the same potato for each potato chip.
To improve this experiment, I should improve the measurements and the qualities of the products. I should start from the beginning to maintain the fair test demands. First of all, I should use the same potato for each potato chip. The surface area of the potato chips should be the same. The length of the potato chips should be increased to 7-cm, so that we can have better results. The greater the length, the greater the length difference. Then I should weigh them all for the mass. I should use different potato chips for masses and sizes, because if the sizes are same, then the masses can be different, because of little difference. After that I should dip them all at same time. I should dip them all in different concentrations but same volume and in same equipment so that these all are dipped properly. I should use greater difference of concentrations of sugar solution, because it gives more different results. When the potato chips are dipped properly, I should start the time for each one. After specific time about one hour, I should weigh them directly. I should not use the filter paper. It absorbs the solution in different quantity. I should record the results of the masses. I should use the scale to three decimal places. Then I should use Varnier Calliper to take the length, because it is more accurate.
To further my investigation, I should try to find the effect of light and temperature on size and mass of the potato chips. I should use different temperature of sugar solution and put then under different light intensities.
For fair test and to further my investigation, I should ignore the anomalous results. In this investigation, I got an odd result, which effected my results, but not much. I should ignore such results and repeat my experiment. I should not only reject these results, but to find out what was the reason behind it, so that I do not repeat the same mistakes. My results are reliable, because they are the same as the scientific theory. They were same as my prediction. I repeated the experiment three times and I use five different concentrations of sugar solution, therefore they are more reliable. They give me a range of idea, which is reliable to the scientific theory. To make my results more strong, I should have more results, so that I can get less range of different results. As my results are reliable, therefore I can have a firm conclusion, although it was not a fair test completely. In this experiment, I got enough results to approve my predictions. I should take more results, so that I can approve or disapprove my predictions with a firm conclusion.
The End
Wais Ahmed
0.6
