Experiment to show osmosis in potato chips in different concentrations of sucrose solution - also investigating how potato chips change in volume and weight when placed in different concentrations of sucrose solution.

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Experiment to show osmosis in potato chips in different concentrations of sucrose solution - also investigating how potato chips change in volume and weight when placed in different concentrations of sucrose solution.

Introduction:

I am going to design and modify an experiment used to show osmosis in potato chips in different concentrations of sucrose solution. I am also going to investigate on how potato chips change in volume and weight when placed in different concentrations of sucrose solution. I will also conduct a preliminary experiment before my final experiment.

Aim:

To investigate the effect of different concentration of sucrose solution on potato chips.

Hypothesis:

I would expect the potato chips to turn flaccid when they are placed in a strong sucrose solution because the water from within the cells will diffuse out leaving the potato flaccid. The potato chips left in the weak sucrose solutions should turn turgid in a weak sucrose solution, due to the water being absorbed by osmosis into the cells of the potatoes, this will make the potato chip larger in size. I should also be able to find some potato chips, which have neither increased nor decreased in size because the concentration in the potato is the same as the sucrose solution, so no mass or length would be gained or lost.

Scientific knowledge:

Osmosis is a type of diffusion, where the molecules move from an area of high concentration to an area of low concentration passing through a partially permeable membrane. When distilled water or a weak sucrose solution or a diluted sucrose solution is used, the water molecules will pass through the semi-permeable membrane into the potato. This is due to the fact that the water is more concentrated outside, so the molecules in the water will move through the permeable membrane, and in this experiment it will pass through into the potato. The potato chip will increase in length, and weight due to osmosis. When a strong sucrose solution or a concentrated sucrose solution is used, the water within the potato will move out of the potato through the semi-permeable membrane, and into the strong sugar solution, of which the potato is soaked in. This will cause the potato chip to shrink in length and mass.

Further information on potato plant cells:

Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in dilute solutions. Turgid means swollen and hard. The pressure inside the cell rises and eventually the internal pressure of the cell is so high that no more water can enter the cell. This liquid or hydrostatic pressure works against osmosis. Turgidity is very important to plants because this is what makes the green parts of the plant "stand up" into the sunlight.

When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become "flaccid." This is the exact opposite of "turgid". The contents of the potato cells shrinks and pulls away from the cell wall. These cells are said to be plasmolysed.

When plant cells are placed in a solution which has exactly the same osmotic strength as the cells they are in a state between turgidity and flaccidity. We call this incipient plasmolysis. "Incipient" means "about to be".

Fair Test

To make sure this is a fair test I will have to keep all the variables constant apart from the concentration. If I did change one of these variables, for example, if one potato chip were 1cm longer than the other there would be more space for osmoses to occur, therefore the test would not be fair.

To make sure the test remains fair I will do all my experiments at room temperature, use the same type of potato, which will be kept at the same size and weight and have been treated in the same way. I will also use the same volume of the solution in the test tube is kept fair. I will use an accurate electronic balance, showing grams to 2dp in this experiment, to ensure even small changes in mass are recorded. I will also keep using this balance throughout the experiment so measurements do not vary due to any change that may be introduced by different scales.
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Key Variable:

Independent variable/s: concentration

Dependant variable/s: mass, length, volume of solution

Controlled variable/s: temperature, size of chip, time

Concentration is an independent variable because we can control and change the concentration to our desired concentration.

Mass, length and volume are dependant variables because our whole experiment depends on these variables, which we can alter and change to a desired amount.

The temperature and time are controlled variables because they should be kept the same for each potato chip and solution through-out the experiment because temperature is a catalyst and may speed ...

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