Water moves from a high concentration gradient of water to a low concentration of water by osmosis - To assess the affect of concentration of water on potatoes we will use different concentrations of mole.

Procedure

In order investigate the effect of the water movement in a concentrated solution we will measure the different types of solutions with the same measured amount of volume. In order to do this we need the following things to be done.  

Apparatus

• 10 cm³ 0 molar diluted sucrose solution
• 10 cm³ 0.5 molar diluted sucrose solution
• 10 cm³ 1 molar diluted sucrose solution
• 3x Boiling Tubes
• Beaker
• Potato
• Knife
• Tile
• 10 cm³ Measuring Cylinder
• Sticky Label
• Cork borer

Diagram

Test Tube

                                                                             Tube Rack

   Potato

                          Different concentrations

Method

1. Firstly put on your safety goggles ensuring that you will not infect your eyes.
2. Get a potato, a cork borer and a tile. Gently push the cork borer into the potato. After you have done that slowly pull the cork borer out with a tube of potato inside. Get something like a pencil small enough to push the potato tube out of the cork borer.  
3. Repeat this 5 times for your each experiment.
4. Make sure that they have the same length and that they weigh the same mass.
5. This is essential for finding out the differences for each experiment. In order to do these get a ruler and a weighing scale. Measure all of them precisely.  
6. With a measuring cylinder measure out 10 cm³  water and pour it in to a boiling tube for the first potato.
7. After you have done that for the next tube, replace a ¼ of the 10 cm³ of water to 0.5 mole of sucrose solution. Therefore you will have 2.5 cm³ of sucrose solution and 7.5 cm³ of water. This will give you 0.175 mole sucrose solution.
8. Add another ¼ of 0.5 mole of sucrose solution for different potato.
9. After you have done the five boiling tubes, put the five potatoes into the tube and seal it with cling film making sure that nothing goes in or out.
10. Wait for 48 hours for the osmosis to occur.
11. Once you have come back to the experiment after 48 hours carefully take out the potato and place it to the weighing scale. Record the data and calculate the differences before osmosis occurred.
12. Repeat this for each experiment.

Safety Issues

We have to be always precautious at all times time prevent any fatal accidents. For example since we are using knives for cutting the potato we have to be precautious to ourselves and others. Goggles must be on at all times during experiment. This prevents anything getting into yours eyes that can lead to permanent disability. Finally we must always stand up at all time to act fast when accidents occur.

Variables

Independent Variable: concentration of water

Dependent Variable: the state of the potato

Control Variable

To make this experiment fair I must keep all the variables the same throughout the whole experiment otherwise the experiment will be irrelevant.

1. Concentration of sucrose solution- the more we increase the sucrose solution the faster the water will move out of the potato. Each potato has the same amount of mass and they will be put into different concentrations of water.
2. Temperature- As we increase the heat of the solution the experiment we speed up. But this will have no effect on the potato since it is the movement of the water the not the speed of the experiment.
3. Type of Plant- we will be using the same potato throughout the experiment otherwise if we used different plants it will give different outcomes.
4. Sizes of Potato- the Potato contain the concentration of water and if we change it this will give a different output. Therefore, it is very important to measure out the length and the weight of the potato, making sure all the potatoes are equal giving out the same output.      

Preliminary Work

I have to take preliminary experiment before I carry out my real experiment. This will ensure that I will get the best results I can get.

• From the Preliminary work I have found out that 0 to 0.5 mole was too little. So for the next experiment I will extent it to 0 to 1 mole. This will give me a wider range of answers to find out how osmosis works.
• I have left my experiment for 7 days which is too long. This has caused the potato to go all mushy and unreliable for the recording. For the real experiment I will be shortening to 48 hours.

Analysis

From my results it has shown me that when there is a higher concentration of sucrose solution, water will move out of the potato. Also when there is a lower concentration of sucrose so the water will move into the potato. We can see from the results 0-0.2 molar is when the water moves into the potato because there is less water in the potato. This makes the cell turgid. From 0.4-0.6 molar, is near to the equilibrium stage. This is when both sides have the same amount of water concentration. So there is no need for any movement to take place. From 0.8-1 molar is when there is less concentration of water outside the potato and more concentration of sucrose, therefore the water inside of the potato moves out into the solution. When this happens the cell becomes flaccid and when there is no more water left, it is plasmolysed destroying the cell membrane and eventually denatures.

From my results I have many evidences to conclude myself that osmosis does occur and my prediction was correct. From my experiment that as I put the potatoes into a higher sucrose solution the more flattened (flaccid) it became. And the lower sucrose I put in the more plump it became. Water moves from a high concentration to a low concentration. This is controlled by the impermeable membranes. This process is essential for plants and animals. For example the root of the plant sucks in the water by osmosis. This happens because there is less water in the root than outside the root. The impermeable membrane controls what goes in and out. The impermeable membrane has tiny holes letting water to get through and other small substances.  

Evaluation

I found the experiment relatively easy because I got the chance to do the preliminary work before the real experiment. I have made relatively accurate results which prove that osmosis does occur. I did not leave out anything that would affect the whole experiment. Measurements I made were very accurate using 0.01g and 0.5mm. I had to put 3 potato cylinders into one tube because there were not enough tubes to go around. If there were then I would know the each individual potato’s previous results. I have averaged 3 potatoes so that in case one of them went wrong I would still the have the two potatoes doing the right thing. Also putting 3 potatoes into one test tube can give different results. This is because if you have three potatoes then there is a bigger surface area to osmosis to take place. We had to do that to every potato in order to make a fair test. If I was using my hand to do the cutting I do not think it would be as effect as using a machine. I have used a ruler and a knife to cut out the potatoes accurately. I had to use a pencil to push out the potato cylinder out of the cork borer because I did not have mounted needle. This could of effect the results because I had pushed the potato resulting a bit squished. I have made a good choice of different concentrations of molars after having learnt that from 0m to 0.5m was not enough. My results have been mostly accurate. I was able to create a line curve for my graph proving that there is a pattern on how osmosis works.

There was one result which I thought was a bit anomalous, the 0.4 m. It was supposed to be below the previous weight and length but unfortunately it gave a different answer. This error could have been caused by misreading the measuring cylinder or I got a healthy/unhealthy part of the potato which has speeded up the process of osmosis. If I had more time I would redo the 0.4 m to double check that the results are correct. I would predict that if I had done it again then it would fit the line curve because as I increase the independent variable I also increase the dependent variable. What I could have done to improve my results would be to put each potato tube in each test tube individually giving a more accurate answer. Also I would handle the potato more gently so that I don’t squeeze out the water which I need for the results.

If I had the chance to carry out a further investigation I would add temperature to it. I predict that as I increase the temperature the faster osmosis will occur. This is because as I increase the temperature the molecules will move faster therefore the water molecules are more likely to go in through partially impermeable membrane. This will show how osmosis works in different weather conditions. By doing this it can give us many interesting and useful results on how osmosis works.