Rate of reaction = change in absorbency/change in time

 Calculation:

To gain an average reading over my results I used the following formula:

        Average absorbency =  Test 1+2+3

                                                           3

eg. 20ºC, at 1min        

 0.13+0.16+ 0.15 =0.15

              3

Also to back up my results I found out what the rate of reaction was for each temperature, using the averages calculated before. I did this by using the following formula:

        Rate of reaction = change in absorbency/change in time         

eg. 100ºC, 4 minutes:

        0.53/4= 0.1325 

Skill C-Analysing Evidence And Drawing a Conclusion

Graph Analysis:

Average absorbency graph:

Looking at this graph shows me the trends that occur in my results. The ability to draw a line of best fit showed that the points lie on a line of positive correlation. 80ºC had the most pigment released after 7mind and with 20°C.

        The 20ºC, 40ºC and 60ºC were all where I thought they should lie. 60ºC released more than 40ºC and that temperature released more than 20ºC.

        Also the line of best fit showed that the amount of pigment released increased as time passed. Which is what I predicted. The reason for this is that more pigment is being released into the surroundings. at 20ºC, 30°C, 40ºC pigment is released at a steady rate and 60ºC. 70ºC and 80°C the speed of absorption has increased.  This explains the steady absorbency as temp goes up. A reason for the pigment escaping could be that the proteins in the cell membrane could get denatured, meaning that the pigment can escape. Therefore at a higher temperature the cell wall becomes unstable quicker and denatured allowing pigment to escape into the water.

        The fact that heat is known to denature proteins could prove that is why the pigment escapes. The graph and table show that there is a greater absorbency margin as the temperature increases. This can be seen when comparing 40°C and 80°C at 5-6 mins 40°C only rises a absorption rate of 3 where as 80°C by 13, and then from 6-7 mins 40°C by 7 and 80°C by 14, I think this is due to the cell membrane being denatured faster due to the higher temperature

Rate of reaction graph:

This graph shows the rate of reaction against time. Using the graph I found that for all but 2ºC the rate of reaction decreased as the experiment went on. However with 2ºC the rate of reaction actually increased as the experiment went on. This is surprising, as I would have thought that the rate would decrease as it did in most cases. E.g. for 80ºC the rate fell from 0.15 to 0.078, and to show the large gap 60ºC fell from 0.04 to 0.017.

        The rates of reactions were in the same order as the amount of pigment graphs, the 100ºC rate is faster than the 80ºC and there is the large gap between them and the lower temperatures.

        I expected the rate to decrease, as there would be less pressure inside the cell as the pigment escapes from the cell. This would mean that the pigment would not escape as fast because it isn't getting pushed out as fast. Also the water potential either side of the cell wall will start to level out which would lower the rate of diffusion of the pigment.

        At first with all, but 2ºC, the rate of reaction is very fast then it starts to slow down. This backs up my theory that the pressure gets less. Because as more pigment escapes out of the cell the less pressure which will slow the rate down. And as there will be lots of pigment at the start then there will be high pressure so the rate of reaction will very fast, as shown in the graph.

Anomalous Results:

When looking at the graph I can see that there are no anomalous results, which could indicate that the experiment was quite precise, but that does not mean that it is accurate. The readings I got might be along the same trend but that trend could miles off the actual value. This normally suggests that it is not down the human error but the equipment used is the cause for error.

        However if I look at the table of results I can see that there are two anomalous results that do not fit in with the trend. This could be down to human or experimental error.

Skill D-Evaluating Evidence and Procedures

Changes to The Experiment:  The experiment was changed to make it easier to take results, by using a full test tube colorimeter with the beetroot on pins to make it quicker to pull out after the short time limit. There would be a increase of pigment released due to the pin being inserted to the beetroot but washing off the excess pigment in the water bath for 2mins beforehand will have reduced the error for this.  

Criticism of Apparatus: