How Does Osmosis Affect Plant Cells?

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Aim:

The aim of the experiment is to find out how the concentration of the solution will affect the rate at which osmosis occurs.  I will use this as a trial run to find out which concentrations and at what time is best to leave the cuttings for the greatest change in mass to occur.

Apparatus:

  • 2 potatoes
  • 2 250ml beakers
  • 25ml of sugar
  • top pan balance
  • no. 9 core borer
  • knife
  • 375ml of distilled water
  • tablespoon
  • stopwatch

Method:

  1. Collect the equipment.
  2. Add 125ml of water and 25ml of sugar in one beaker and 150ml of distilled water in the other.
  3. Using the size 7 core borer carefully cut 10 equal 3cm strips out of the potato.
  4. Using the scalpel cut the cuttings to 5 grams and 3cm stripes, making them as close to one another as possible.
  5. Mix the solution with the tablespoon, then add 5 pieces of potato to each beaker, while timing the length of time they are in for to the set times.
  6. At every set time measure the length and mass of all the potato cuttings and put it back into the beaker.
  7. Record the results into a coherent table.

Fair Test:

To make my experiment a fair test I will keep the potato cutting at the same length and mass.  I will use the same size borer, no. 7, throughout.  My cuttings will be taken from the same type of potato and will contain no peel.  The volume of the two liquids must also be kept equal.


Table of Results:

SUGAR SOLUTION (started at 10:45am)

WATER SOLUTION (started at 10:45am)


Conclusion:

My results basically tell me that the greater the time in the sugar solution the more water is lost and the lighter the potato cuttings become.  My results from the test in the sugar solution were fairly accurate with no anomalies as seen in the graph, but my results in the water solution had a few anomalies.  As time went on there was a consistent increase in mass and length, but once the cuttings had been in for 24 hours there was a major decrease in mass and length which makes the results inaccurate.

For my main experiment I have decided to use 24 hours simple because I think this is the sensible length to leave the cuttings.  I believe that whatever is going to happen will happen within this period of time and therefore making it the most sensible time to leave the cuttings.

When analysing my results I decided to use my measurements of the mass of the potato cuttings as a measurement of osmosis.  This was decidedly purely on the theory that it will be easier to measure mass more accurately on a digital top pan balance which leaves no room for human error, unlike the measurement of length using a ruler which can not be entirely accurate.

Evaluation:

 

This experiment was not a great success.  I didn’t gain the best results possible and haven’t used this preliminary work to its full potential as an aid for my main experiment.  I was able to gain knowledge of what times were best to leave the potato cuttings in the beakers for, but I was unable to really gain a great knowledge on the effect of a range of concentrations of solutions on the potato cuttings.

The reason I chose the times I chose was because at these times I was able to revisit the beakers without disturbing lessons and I think they needed to be left a long enough period of time for anything that was going to happen, to happen.

In my main experiment I will use a known range of concentration, ranging from 0molars to 1M and a greater number of test solutions (e.g. 0, 0M, 0.2M, 0.4M, 0.6M, etc.) to help improve the accuracy of my graph with more results to plot, therefore giving a more reliable line of best fit. I will do a number of trials to improve the reliability of my results, through calculating averages and I will find a more accurate way to cut the potatoes to get them all at a similar mass.



Aim:

To find out how altering the concentration of the sugar solution will change potato samples as a result of osmosis.

Apparatus:

  • Measuring cylinders         - 100ml

-  50ml

                                -  10ml

  • 1 large potato
  • Forceps
  • Six 100ml beakers
  • Sticky back labels
  • Distilled water
  • Sucrose solution 1M
  • No. 7 core borer
  • 2 tiles
  • Some paper towels
  • Ruler
  • Top pan balance (to 0.01g)
  • Scalpel
  • Cling-film
  • Pen
  • Paper
  • Stopwatch

Method:

I mixed the sugar solutions as follows in the table below:

(Remember when measuring out the solutions to use the correct scaled measuring cylinders and to measure from the meniscus, the dip, of the liquid to make your solutions more accurate and correct to the nearest ml, e.g. when measuring out the solution for beaker 3, I firstly weighed out 40ml of distilled water using a measuring cylinder of scale 1-50ml and then I accurately measured the other 8ml using a measuring cylinder of scale 1-10 then added them to one another and put them in the beaker.  When measuring out the sugar solution I used a measuring cylinder of 1-50, measured 30ml, then using a measuring cylinder of scale 1-10 measured the further 2ml and added these two measurements together and mixed them into the distilled water in the beaker.  I did this with each solution in turn).

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When my solutions were mixed I collected 1 large potato.  Placing it on a cutting tile (which provided a stable surface to cut on).  I cut 12, sized 7, cylinders of potato, being careful when using the core borer and directing it away from myself, to avoid cutting myself.

Using a scalpel, I carefully removed any peel from the edges of potato (as it could lead to unfair testing due to the different plant cells in peel and in the actual potato – see table of variables).  Once I had 12 cylinders of the same length, 3cm, I ...

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