Osmosis in Potato's

Osmosis in Potatoes (To show how osmosis in potatoes takes place)

Introduction:

Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration, this basically shows us that osmosis is a type of diffusion but in osmosis there is only the movement of water molecules from a region in which they have a higher concentration to one in which they are in lower concentration of water molecules. This basically means that the net movement of the solvent is from less concentrated (hypotonic) to more concentrated (hypertonic) solution which tends to reduce the difference in concentrations. This takes place through a partially permeable membrane e.g. that of an animal. Osmosis takes place in cells and can also take place in solutions. When a cell is submerged in a glass of water, the water molecules pass through the cell membrane and the process of osmosis takes place. The cell membrane is selectively permeable, so only necessary materials are let into the cell and waste products are given out. It usually occurs in plant cells and animal cells e.g. in humans when water moves from the digestive system into the blood stream and in plants when water goes from the soil surrounding the plant into the root hair cells and then to the cytoplasm. The energy which drives the process is usually discussed in terms of osmotic pressure. This is defined as the energy required to maintain an equilibrium. When osmosis is no longer taking place this means that an equilibrium or an isotonic point has been reached telling us that there are an equal number of water molecules on either side of the membrane. Osmosis provides the primary means by which water is transported into and out of cells. The turgor pressure of a cell is largely monitored by osmosis, across a cell membrane, between the cell interior and its relatively hypotonic environment.

Figure 1: Shows us how osmosis takes place within a liquid.

There are many factors that can affect it such as the concentration of the solutions can have a big difference in the rate of osmosis, the room temperature, and the area or volume over which the osmosis is to take place. If there is a greater surface area through which osmosis is to take place then the rate of osmosis will take place faster, whereas if the surface area is restricted osmosis will take place slower.

I am trying to investigate the rate of ...

This is a preview of the whole essay

Figure 1: Shows us how osmosis takes place within a liquid.

I am trying to investigate the rate of osmosis of water molecules in a potato that has been placed inside a sugar solution. Using the definition of osmosis that has been given above I would predict that in the sugar solutions that are more concentrated there is a more likely chance that the water molecules will move from inside the piece of potato into the sugar solution, but if the sugar solution contains more water molecules then the potato that has been placed in it the water molecules will diffuse into the piece of potato until an equilibrium has been reached. This is because the water molecules move from a region in which they have a higher concentration to a region where they are in lower concentration.

Hypothesis:

Trial Run:

Before doing the actual experiment we decided that a trial run should take place to determine what factors could or shouldn’t be changed. Many different methods could have possibly been used and we could have experimented with different types of factors other than just the concentrations but by experimenting with different types of concentrations we learned how this could also effect the possibility of osmosis occurring in cells. The conclusion drawn from this trial run was that we could change the temperature at which the experiment is kept, the surface area of the potato, the concentrations of the sugar solution we use and the duration of the time that the piece of potato is kept in the solution.

During the trial run we only used one piece of potato and due to this out results were not as accurate so we decided that doing repeats the second time we do the experiment would be good because our results may be more precise as compared to the trial run. We also decided to change the size of potato pieces being used because a large piece of potato was unavailable. In the trail run we used one piece of potato per solution which was dug out using a size 6 cork borer and a ruler to make the length 3cm long. The piece of potato was kept in 3 different types of solutions which are given below as well as the changes in mass and the percentage change:

I also decided to keep the temperature the dame as it was kept at room temperature during the trial run.

I am going to change the concentrations of sugar solution that will be used and keep the temperature at which the experiment will be kept will remain constant. I decided that changing the size of the potato would be best because it would be easier to place three pieces of 2cm potato in one test tube containing the solution as well. We are planning on doing repeats so that the results are more accurate and this will help us find out the rate of osmosis more precisely. We will be measuring them before immersing them in the solution and after taking them out of the solution.

Equipment used:

Sugar solution of 2M
Water
Cork borer – size 6
A ruler cm/mm
3 pieces of potato
Timer
Measuring cylinder
White tile
3 test tubes
Test tube rack

Method:

Cut eighteen pieces of potato which are each two centimetres long using a cork borer and cm/mm ruler.
Weigh each piece of potato in grams.
Place 3 pieces of potato in each test tube.
Mark the test tubes either with numbers or in some method which will help us know which test tube contains what solution.
Place the test tubes in a test tube rack.
Add sugar solutions using the concentrations table shown below.
Place at room temperature and check up on it later.
Take each piece of potato and weigh it.
Find out difference in both measurements and determine the rate at which osmosis takes place.
Plot a graph showing the rate of osmosis against the concentration of sugar solution used.
Determine the gradient of the line placed on the graph.

Concentrations used:

Results table:

Analysis:

My data showed that when the sugar solution is concentrated the piece of potato which is placed inside it tends to loose water and this can be seen when the measurements of its mass are compared to one another. This is not the same case when a very dilute sugar solution has been used. As is the case with some of the solutions that were used, the pieces of potato that were placed in hypotonic solution came out with a bigger mass as compared to the previous measurements. This proves that the rate of osmosis can greatly be affected by the environmental factors such as the temperature of the surroundings in which the experiment is to take place and the concentration of the solution inside the medium, in which osmosis is to take place.

Conclusion:

I would have to conclude that the experiment was successful and demonstrated to us how osmosis takes place as well as showed us what factors can possibly affect it. The potato in which there was more water then their surrounding solution became flaccid and the potato piece in which there was less water than the surrounding hypotonic solution became turgid as a result of losing water to the solution.

Evaluation:

I think my results were accurate because there was a notable difference in the results when they were taken. Major changes in osmosis only take place when the experiment is kept over an extended period of time. Although I did the repeats in the same test tube which helped me to make sure that the concentrations were kept the same, however I think it would be better to do the repeats separately but due to the limitation of having less test tubes we had to do the repeats in the same one. I think it would be better to use separate test tubes because in this experiment the sides of the potato pieces were in contact with each other and that nay have affected the osmosis that was taking place as the surface area may have been decreased due to this.

If they were kept separately osmosis would have taken place into the piece of potato from all sides and that would have had a great effect on the changes that take place.

I think the potato measurements were taken as carefully as possible and that helped my results to be as accurate as possible. The measurements of the mass were taken in two decimal places and that made my results as precise as possible. The cork borer was size 6 and helped to make cylindrical measurement of all the pieces as close as possible to each other, after that a ruler was used to determine the length. This made it as accurate as possible because all the pieces were the same. Using samples from the same piece of potato may have helped however with the experiment because sometimes sugar concentrations largely vary in different parts of the same potato.

- shows coursework