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CIE AS Biology (9700) 2019-2021 Revision Notes

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2. Biological Molecules

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Page 7

Making serial dilutions

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CIE AS Biology (9700) 2019-2021 Revision Notes

savemyexams.co.uk

2. Biological Molecules

YOUR NOTES

⬇

© 2015-2021 Save My Exams Ltd

CIE AS Biology (9700) 2019-2021 Resources

REVISION NOTES 

 

  TOPIC QUESTIONS 

 

  PAST PAPERS

Page 8

Colourimeter

A colourimeter is an instrument that beams a specific wavelength (colour) of light through a

sample and measures how much of this light is absorbed (arbitrary units)

They provide a quantitative measurement

They contain different wavelengths or colour filters (depends on the model of colourimeter),

so that a suitable colour can be shone through the sample and will not get absorbed. This

colour will be the contrasting colour (eg. a red sample should have green light shone

through)

Remember that a sample will look red as that wavelength of light is being reflected

but the other wavelengths will be absorbed

Colourimeters must be calibrated before taking measurements

This is completed by placing a blank into the colourimeter and taking a reference, it

should read 0 (that is, no light is being absorbed)

This step should be repeated periodically whilst taking measurements to ensure that

the absorbance is still 0

The results can then be used to plot a calibration or standard curve

Absorbance against the known concentrations can be used

Unknown concentrations can then be determined from this graph

 

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