Calibration curve

International Baccalaureate Biology

Bio Lab 4 – Calibration Curve

October 6, 2008

Calibration Curve

Aim: In this experiment the basic aim is to make a calibration curve for the concentration of glucose

Hypothesis: As the glucose concentration increases the time taken for it to turn colourless will decrease.

Variables: Independent- Concentration of Glucose

Dependant- Time taken to de-colourize the potassium

Constant- Amount of sulphuric Acid and the other material used

Apparatus:

1 stop watch
11 test tubes
1 test tube stand
11 rubber stoppers
150ml of glucose solution of 10g/dm3
30ml of 0.01mole potassium permanganate solution
60ml of 1M sulphuric acid
4 plastic syringe of 20ml
4 beakers
10ml distilled water in wash bottle
Marker (pen)

Method:

Obtain the 11 test tube and places them in the test tube stand.
Label each test tube from 0 – 10 using the marker.
Using the syringe add different quantities of glucose in each test tube. In the test tube labelled ‘0’ add no glucose. In the test tube labelled ‘1’ add 1ml of glucose, now in the same way continue this process until u have filled the last test tube with 10ml.
Now different amounts of distilled water must be added into each test tube using a different syringe. It follows the same procedure as glucose. In the test tube labelled ‘0’ 10 ml of distilled water should be added. In the test tube labelled ‘1’ 9 ml of distilled water should be added. In the same way this process must be continued until the last test tube ( I.E. test tube labelled ’10’) no distilled water is added. Therefore the total amount of liquid in each test tube is 10ml so far.
Now using the third syringe add 5ml of 1M concentration of sulphuric acid into each test tube.
Now 2ml of 0.01M potassium permanganate solution must be added in each solution. When adding the potassium into the first test tube you must start the stopwatch at the same time and keep the stopwatch running.
Now continue adding the potassium to each test tube, after adding the potassium place the rubber stopper onto the test tube and shake well, then record the time when the potassium permanganate solution was added.
After adding the potassium permanganate, the solution turns purple. Once all the test tube have been added with potassium permanganate solution, observe each test tube and record the time for each test tube once it de-colourises.
Make a table with the results obtained.

Fair Test-

Distilled water was used instead of tap water this is because it is more pure and has less contamination.
A stop watch was used for a more precise and correct method in tracking the time.
A syringe was used so that the amore precise amount of solution could be added.
Different syringes were used for each solution so the solution is not contaminated.

Safe Test-

Each beaker was handled carefully so that it didn’t fall and break.
When shaking the test tube we made sure that it didn’t fall ...

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Fair Test-

Distilled water was used instead of tap water this is because it is more pure and has less contamination.
A stop watch was used for a more precise and correct method in tracking the time.
A syringe was used so that the amore precise amount of solution could be added.
Different syringes were used for each solution so the solution is not contaminated.

Safe Test-

Each beaker was handled carefully so that it didn’t fall and break.
When shaking the test tube we made sure that it didn’t fall and break.
When using the syringe we made sure the liquid did not come in contact with any of us.

Results- The Time Taken To De-Colourise the Potassium with Different Concentrations

Graph:

Conclusion: As we can by looking at the graph and our results is that as the glucose concentration increases the time taken for the liquid to turn colourless decreases, therefore this also proves that our hypothesis has been proved correct. In other words we can say that when glucose was more concentrated the potassium decolourised faster than when the glucose was less concentrated.

Evaluation: This experiment was not a 100% accurate there were many human errors that occurred and these could have led to the inaccuracy to the results, which may have also caused some anomalies in the results. They may not have been huge errors but there were many small errors that may have caused the change. The first error was that the the amount of liquid added into the beaker using the syringe may not have been completly accurate as the reading measure would not have been completly accurate. Also when taking 3ml or 5ml or any other odd number. This would tend to be more inaccurate as the marking were not on the syringe. This kept occurring when adding the solution into the test tube. Another big error was that when the potassium permanganate was added the stopwatch time must be started at that exact same time, and in other occasion the time must be noted when the potassium was added, but it was most unlikely that both of this ever occurred simultaneously as humans tend to make errors. Another errors is that we did not know what the exact moment would be when the solution would turn colourless, at some occasion the solution was close to colourless but not completely colourless. Therefore the point is that it was hard to tell when the solution was completely transparent.

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