Osmosis Investigation

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Osmosis Investigation

Aim:

The aim of this investigation is to investigate if different concentrations of sucrose solution with affect osmosis in the potato cells.

Introduction: What is osmosis?

Osmosis is how water enters a plant by its roots. Many surface cells of the plant's roots have 'projections' called root hairs. The purpose of these are to increase the overall surface area of the roots so this enable as much water to enter the plant as possible so osmosis can take place. Osmosis is the process by which water molecules move from an area of low solute concentration, the soil, to an area of high solute concentration, the plant, through a semi-permeable membrane.

See Diagram 1

Diagram 1: Diagram of Osmosis taking place in the cells of a leaf

Preliminary Investigation

To help me get a better understanding of the process of Osmosis and to help me to come to a sensible and realistic scientific prediction, I carried out a preliminary investigation. In this investigation we took 10 potato chips, carefully cut to the same size, and placed them in separate plastic test tubes. Then we picked a solution of sucrose solution out of 1M, 2M, 0.5M or 0.25M and poured an equal amount into each test tube and left for 24 hours. We carried this experiment out with several different solutions of sucrose solutions, using the potato chips because we wanted to observe the changes that took place in the potato cells while they were in the sucrose solution, and if the different concentration had any effect on the growth.

We carried this preliminary investigation out on the potato chips using the solutions 1M, 2M and 0.25M. Here are the results tables for each sucrose solution.

O.25 M Solution

M Solution

2M Solution

Using the Information I have gathered form carrying out the preliminary Investigation I know have the knowledge to help me make a scientific prediction about the effect different solutions of sucrose solutions has on osmosis in the potato chips.

Scientific Prediction:

I predict that the higher the concentration of sucrose solution, which the potato is placed in, the more the potato will decrease in size. This means that the lower the concentration of sucrose solution the more the potato will increase in size.

I predict this because I know that osmosis, the movement of water molecules, takes place from an area of low solute concentration to an area of high solute concentration.

If you place a piece of potato in a high concentration of sucrose solution and leave it for 24 hours the water molecules in the potato, which is a low solute concentration compared to the sucrose solution, will travel through the semi-permeable membrane into the high solute concentration of the sucrose solution.

As the water molecules have diffused from the potato and into the sucrose solution it results in the potato chips loosing molecules and decreasing in length and size.

However if you place a piece of potato in a low concentration of sucrose solution the opposite will happen. The potato is now the area of high solute concentration because the sucrose solution is much weaker as it has more water present because it is a lower concentration.
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The water molecules in the low concentration of sucrose solution will diffuse through the semi-permeable membrane into the potato as it has a high solute concentration. This causes the potato to increase in size and length

When the cells absorb water by Osmosis they swell up. This causes a build-up of pressure, called turgor pressure. The cell wall of the potato or plant is made up of tough inelastic cellulose and this tops the cell from swelling too much. The build up of pressure inside these inelastic cells causes them to become large and firm (turgid) and ...

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