Investigation of Osmosis in Potato chips

Osmosis

In botany and chemistry, osmosis in a flow of one part of a solution through a membrane while the other parts of a solution are blocked and unable to pass through the membrane. Experimenting may be needed to determine which membrane permit selective flow, or osmosis, because not all membranes act in this way. Many membranes allow all or none of the constituents of a solution to pass through, only a few allow a selective flow. In a classic demonstration of osmosis, a vertical tube containing a solution of sugar, with its lower end closed off by a semi-permeable membrane that may be used for such a demonstration is the membrane found just inside the shell of an egg, (the film that keeps the white of the egg from direct contact with the shell.)

The movement of water molecules from a region of their high concentration to a region of their low concentration through a differentially permeable membrane. Osmosis pressure- the pressure a solution generates when enclosed within an osmometer and allowed to come to equilibrium with pure water.

If a hyper tonic solution is separated from a hypnotic solution by a differentially permeable membrane, a net flow of water molecules occurs through the membrane from the hypnotic to the hyper tonic solution. When there is no longer a net flow of water both solutions are isotonic with each other. The higher the solute concentration the higher the osmotic pressure (OP). However this OP is a potential value and is more correctly termed osmotic potential P by convention, P is given a negative sign.

Factors affecting Osmosis

• Making the surface area of the chip bigger can increase the rate of chemical reactions involving a chip. Using a smaller chip can do this because there is more exposure of the area to the water.
• If a reaction involves a solution, increasing the pressure of the solution will increase the rate of reaction.
• By increasing the concentration it can increase the rate of osmosis because diffusion is taking place.
• Temperature also affects the rate osmosis; a 100c in increase in temperature will roughly double the rate of reaction, therefore it will increase the rate of osmosis.
• The type of potato can also affect the rate of osmosis because it has a different permeable.  Like plants, light give energy, which in turn will increase the rate of osmosis.

Aim:-

        

• To see whether a potato chip would be affected by the concentration of the solution.
• To see whether the potato chip would change in length and width.

Prediction:-

• The higher the concentration, the shorter the chip will become.
• The higher the concentration, the lighter the weight.
• The higher the concentration, the softer the chip will become.

• The higher the concentration, the longer the chip will become.
• The higher the concentration, the heavier the weight.
• The higher the concentration, the harder the chip will become.

Fair test:-

• The length/weight of potato chip will be kept constant.
• The concentration will vary from 0 m-1.0 m.
• The time that the chip will be left in the concentration solution, which the time will be kept the same.
• Keeping the heat constant.

Safety:-        

        

• Goggles were worn.
• Aprons.
• Sleeves were pulled up (when necessary)
• Handles sharp objects with care (holding a knife downwards by your side)
• No running.
• Long hair was tied back.
• Worn gloves (when handling hazardous chemicals)
• Take care of hazardous chemicals.

Equipment:-

        

• 10 test tubes
• 2 x 250mlsbeaker
• I x 100 ml measuring cylinder
• Weighing balance
• Scalpel
• Corer
• Plunger

Method:-

A sucrose solution ranging from 0.0 M to 1.0 M were put into test tubes which were placed on a test tube rack. A corer and plunger were used to cut cylindrical shaped potato chips all from the same potatoes. Each chip was measured so as to have them all the same weight and same length.

A chip was placed in each test tube containing the sugar solution. These procedures were repeated once again. All the test tubes were kept together at the same temperature for 24 hours. After 24 hours had elapsed, the chips were dried. The new weight and length of each chip was measured and recorded in a table.

Results and Discussion:-

There is a great change in length of 2mm when it is put into the sucrose solution. The concentration of water outside the potato chip is larger than the concentration of the water inside the potato chip therefore the water moves into the potato chip by the process of osmosis whereby water moves from a high concentration to a low concentration.

When the sucrose solution increase, the change in length decreases and vice versa. If the concentration of sucrose solution decreases, water leaves the potato chip by osmosis.

At 0.28M, the amount of water entering the potato chip is equal to the amount of water leaving the potato chip therefore an isotonic situation is set up. This is where the concentration inside and outside the potato cells are the same.

Above 0.28M there is a great loss of water from the potato cells that means that the concentration of water within the potato cells is greater than the concentration of water outside the potato cells so water leaves the cells by osmosis hence the potato cells wilt. Conversely below 0.28M the cells shows signs of turgidity (expansion). The maximum gain in length is 2mm at 0M sucrose and the maximum in loss is 5mm at 1.0M sucrose.  

It is clear that the gain in length was a lot less than the loss of length because potato cells are surrounded by a cell wall and so when the cells take in water the cell wall restricts how far the cell membrane can expand, without the cell wall, the cell will take in the water until it explodes. Great loss of water means that all the water is leaving the potato cells and leaves a minimum or if any left. The cell is full of very concentration constitution (sugars, salts, etc...) Reference to weight, at 0M there was the highest increase in weight and this was done to the fact that the cell was taking water, therefore this increase in weight was because of the water taken in. As the sucrose concentration increases, the weight decreases because water leaves the cells, as the concentration increases 0.4 of sucrose solution. The amount of water entering is equal to the amount of water leaving (isotonic). By then, it is left with the original weight that it started with.

Beyond 0.4M of sucrose solution, there is a continuous loss of weight. This is due to the water leaving the cells by osmosis. The maximum loss in weight is 6.0g. Just a fraction below 0.28M in sucrose solution the change in weight and length was exactly the same value, which means that osmosis was affecting these two in the same way. When the changes in length and weight are compared, the loss in weight is significantly smaller than the loss in length, this is because the change in length is governed mostly by the elasticity of the cell membrane and also by the cell wall which restricts how far the cell membrane can take water in. The small change in weight maybe seen in terms of there being no change in the basic structure of the potato chip. There’s only a change in the movement of weight so the mass of the potato chip is constant in effect and the weight is affected by the movement of water coming in and out of the cell.

Conclusion:-

I accept my prediction: “The higher the concentration, the shorter the chip will become” and “The higher the concentration, the lighter the chip will become”, these were shown that they were correct.

Concluding off the experiment, the graph of results shows that both the length and weight are expanding at the low concentration of solution, but as the solution gets stronger, the chip become flaccid/limp. You can see that with respect to length, the size changes at a rapid speed, while the weight slowly changes. This shows that the concentrated solution may have affected the length of the chip more than the weight, or at the time of the experiment, the temperature or pressure may have also affected the chip. The graph shows that the potato chip absorbed the sucrose solution which means that the inside concentration will be higher than the outside concentration, this is called hypertonic. When one side of the concentration is lower, it is called hypotonic.

Evaluation:- 

If we did not perform the experiment, it could be correct to say that a rise in temperature can cause an affect on the rate of osmosis or the size and mass of the chip. When the temperature reaches a certain point, the proteins are denatured.

I enjoyed this osmosis experiment, it made me wonder what would happen to the chip after a certain time. Now I know that the chip became limp-almost like a plant when it doesn’t get enough water. In the results, it showed a break-even point. This is where both the length and width become the same. If I were to do the project again, I would determined how the surface area is affected by osmosis (concentration of sucrose solution being constant.) If the graph was plotted using the ‘surface area’ and the ‘changes of the potato chip through osmosis’, I think that, as a line graph, the line would increase at a steady speed in a straight line. If the ‘changes of the potato chip’ was plotted with the temperature, I think that the line will increase gradually until it reaches it’s peak and then drop dramatically down.

The results of my graph look correct, there were no strange occurrence and I know that my graph is correct because my prediction matched the fact that when the sucrose solution was increasing, the potato chip would decrease in size and vice versa.

Bibliography:-

Microsoft Encarta 2000

The Dorling Kindersley children’s Encyclopaedia: Kramer, Ann

Published in Great Britain in 1991

The History of Science: Stewart, Robert W.

Sam’s Publishing: 1995

Science: Designed by Armitage, David

Roger Coote Publishing: 1994, 1995