Biology Coursework: Osmosis Investigation - page 2
Keywords: biology coursework osmosis potato potatoes sucrose molar mass change
By ruth on 08/11/2006 17:19:48
Level: GCSE Key Stage 4 (Years 10-11)
Page Number: 2 of 7 pages: 1 2 3 4 5 6 7
and in the potato, will be when the solution is 0.5 molar. This means the concentration of the potato itself I predict to be 0.5 molar.
Here is a graph of what I predict the results to be:
Preliminary Work:
I chose to, before my experiment; try out three different molar solutions, 0.0, 0.5 and 1.0, so that
I could set the upper and lower limits of my range. It also enabled me to evaluate my method and make changes for the real experiment. Here are the results of my preliminary experiment:
Concentration of Sucrose Solution/m Weight Before/g Weight After/g Change in Weight/g Percentage Change of Weight/% *
0.0 3.05 3.18 +0.13 4.3
0.5 3.42 3.45 +0.03 0.9
1.0 3.92 3.80 -0.03 -3.7
*Calculated by the following formula:
(change in weight (g) / weight before (g) ) x 100
These results of my preliminary have made me realise the general trend of what happens between 0.0 and 1.0 molar sucrose solutions, and have informed me that the point of equilibrium is just under 0.5 molar. I have decided following these findings to investigate the percentage change in mass in 0.2 intervals, therefore 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 molar solutions will be made up. We left the preliminary experiment for about twenty minutes and I decided that this wasn’t sufficient time and I would leave my real experiment for ninety minutes. This was as the results weren’t totally accurate and I thought I would gain more accurate results leaving the potato for a longer time. Also in the preliminary experiment I found it not very clear to find out which piece of potato had been in which solution when re-weighing them as I could not easily differentiate from the three, and so decided to in the real experiment use coloured pins so I could tell which was which and make sure I recorded the correct weight change. Other equipment I will use is firstly tissue paper, I realised following this experiment that the results may not be very accurate as I did not blot them to remove excess water, and so I will do this in the real experiment. Also I will use cling film to stop evaporation of the solutions in the next experiment.
Range:
In my experiment I will make
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