An experiment to investigate how the effect of varying concentrations of salt solutions play on the movement of water in a potato.

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Fahim Talukder 11TS

preliminary experiment

An experiment to investigate how the effect of varying concentrations of salt solutions play on the movement of water in a potato.

aim

The aim of this experiment is to try and find out how different concentrations of salt solutions affect the osmotic activity in a potato tissue. Thus we will be able to find out if the mass of the potato has increased or decreased in the different concentrations of salt solution.

Apparatus

  • A Single Fresh Potato
  • McCarthy Bottles = x 5
  • Corks = x 5
  • Water = 20cm3 x  5
  • 2 Molar Salt Solution = 150cm3
  • Test Tube Rack to hold 5 test tubes
  • Pipette
  • Scalpel – To cut the potato tubes into cylinders
  • Weight Measuring Scales
  • Ruler – To measure the potato cylinders accurately to 2cm long.
  • Cork Borer
  • Cutting Board – Where the potato can be placed and cut safely
  • Marker Pen will be used to write on the test tubes so that I will be able to distinguish between the potato cylinders and determine which salt solution is in which test tube.

Detailed Info on how to prepare the solutions required

Just like my final experiment, in this preliminary experiment I increased the concentration in my five bottles by 0.5 moles, until it reaches 2 molar.

1 mole in 1 litre requires 58.5g of salt to be dissolved in it. Therefore as 1 litre is 1000 cm3, I was thus able to take these into account and do my measurements.

0 Moles = Pure Water

0.5 moles in 20 cm3 of water = 58.5/ 125 = 0.468g of salt

1 moles in 20 cm3 of water = 58.5/100 = 0.585g of salt

1.5 moles in 20 cm3 of water = 58.5/75 = 0.78g of salt

2 moles in 20 cm3 of water = 58.5/50 = 1.17g of salt

Diagram

                  Cork

                  Potato Cylinder

        

                       (0 Molar Solution)

                                                 

    Mc McCarthy Bottle

I have drawn a diagram of what the experiment will look like seen above. I have been given the best equipment to carry out this investigation thoroughly. Within each of the McCarthy bottles contains the different molar solutions with the potato cylinder as you are able to see above. I will be using the concentrations of 0 Molar, 0.5 Molar, 1 Molar, 1.5 Molar and 2 Molar. The experiment will take place over the time-span of twenty-four hours. After twenty-four hours the results will be recorded and the apparatus would be washed and cleared

method

  • A range of salt solutions will be prepared from 0 molar to 2 molar
  • Using a cork borer I shall cut out potato tissue from the potato itself, five potato cylinders are required so the experiment can proceed.
  • Using a scalpel and a ruler the potato pieces have to be cut, so they are 2cm long. Here I have to be careful when cutting the potato so I don’t cut myself.
  • After I have cut the pieces the potato cylinders have to be weighed one by one and the results have to be recorded.
  • The salt solutions have to be made and entered in the Mc McCarthy bottles.
  • The potato cylinders are inserted inside the Mc McCarthy bottles.
  • I will then record which bottles have what solutions and the weight of the potato cylinders, also with a marker pen I shall write on the test tubes which potato has which concentration.
  • I will then put corks on top of the Mc McCarthy bottles so the potato and solutions don’t spill out.
  • Then the Mc McCarthy bottles will be left for 24 hours
  • After 24 hours I shall take out the potato cylinders and weigh them.
  • I shall then record the results and see if the mass of the cylinders has increased or decreased.

For this preliminary experiment 5 potato cylinders will be going into one of the salt concentrations, i.e. 1 potato cylinder will be inserted in 0 Molar, another one in 0.5 and so on until the last potato is put into the 2 Molar concentrations.

Results

These were the results gained after the potato cylinders had been left in the McCarthy bottles for 24 hours.

Analysis of results

From the results, we see that as the molarity increases, the percentage difference decreases and with very high concentrations becomes a negative value. However I have found an anomaly of 0.5 M which has dipped to a negative value of percentage difference. Therefore, from my results, I am stating that with concentrations that are higher, there will be a negative percentage difference in the mass of the potatoes. This supports the process of osmosis, which occurs in the cells; when the external solution is greater, water moves out of the cell. Therefore, there must be a decrease in size. Similarly, when the concentration of salt solution is greater, the potato cylinders decrease in mass.

First of all we are able to see that the percentage difference at first is positive, therefore, water moves into the potato cells in order for equalization to occur. This is why the potatoes will increase in mass and thus, a positive percentage difference. I believe this will happen in my final experiment also.

conclusion

From this preliminary experiment a number of improvements can be made to make the results more reliable and accurate. First of all I believe I should have obtained more results and with those results should have gained an average. Therefore for my final experiment for each molarity I shall have 3 potato cylinders and by having those results I can gain an average. I could also change one of the variables such as temperature, and see what effect temperature plays on the osmosis of a potato. I could leave 5 sets of 5 potatoes could be placed in water at 10 degree Celsius, 20, 30, 40 etc. The concentration was only measured by a pipette which could have given me wrong results; therefore I could collect the salt concentration via titration.

An Experiment to investigate how the effect of varying concentrations

of salt solutions play on the movement of water in a potato.

Aim

The aim of the experiment is to try and find out how different concentrations of salt solutions affect the osmotic activity in a potato tissue. I will achieve this by using potato cylinders and placing them in different concentrations of salt solutions. Therefore we will be able to find out if the mass of a potato has increased or decreased in different concentrations of salt solution.

Apparatus

  • A Single Fresh Potato
  • McCarthy Bottles = x 5
  • Corks = x 5
  • Water = 20cm3 x  5
  • 2 Molar Salt Solution = 150cm3
  • Test Tube Rack to hold 5 test tubes
  • Pipette
  • Scalpel – To cut the potato tubes into cylinders
  • Weight Measuring Scales
  • Ruler – To measure the potato cylinders accurately to 2cm long.
  • Cork Borer
  • Cutting Board – Where the potato can be placed and cut safely
  • Marker Pen will be used to write on the test tubes so that I will be able to distinguish between the potato cylinders and determine which salt solution is in which test tube.
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Diagram

                  Cork

                  Potato Cylinder

        

                       (0 Molar Solution)

                                                 

    Mc McCarthy Bottle

I have drawn a diagram of what the experiment will look like seen above. I have been given the best equipment to carry out this investigation thoroughly. ...

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This is an extremely detailed investigation that shows a good understanding of the scientific process. 1. The preliminary test is conducted well. 2. The introduction section is very well researched and extremely well written, although the sources should be referenced. 3. There has been a great deal of care taken in sections such as the variables, method and safety. 4. The analysis of the results needs to be readdressed and anomalous results left out. 5. The evaluation shows a good understanding of the scientific process. 7. There is a great deal of repetition in this report that should be removed. ****(4 stars)