Need Help Identifying Errors In Experiment

Hello everyone.

I have to do a write up about an experiment I did in my AS Level Biology class. Here is an overview of the experiment.

Ivestigating the Effect of Ethanol Concentration on the Permeability of Beetroot Cell Membrane

1. You will need to make up a Serial Dilution of Ethanol to give a range of concentrations from 0% to 100%

2. Put a 1cm length of beetroot core into each tube and leave for 20 minutes.

3. Mix well then pour the liquid into a second labelled tube.

4. Measure the absorbance of each tube in a colorimeter using a blue/green filter (490nm) after zeroing the colourimeter with the distilled water.

Equipment Used:

•

Knife (cutting the beetroot)

•

Ruler (measuring beetroot slices)

•

Pipettes (for measuring liquid)

•

Colourimeter

•

Cuvette (those weird cuboids with a serated side on them that get placed inside the colourimeter)

In my write up, I have to include details on Random and Systematic Errors. I know what these are but can anybody suggest some that I can write about? I have real trouble spotting them.

Many big thanks.

Reply 1

HannahUVM

11

How about the accuracy of the cutting of the beetroot pieces for a random error.
The calibration of the colorimeter could lead to a systematic error if it wasn't done right.
Maybe there could be measuring inaccuracies too if you are using a test tube to measure volumes of liquids because they are horribly inaccurate.

Reply 2

getfirefox

OP

2

Thanks for the help.

Anyone got any others?

Reply 3

Revd. Mike

17

What type of pipettes were you using? If you're talking about the microlitre precision kinds (with the piston bit) then check they're within calibration, correct tip was used, haven't been misindexed etc, as all of those things can lead to systematic errors. If you're talking about the glass/plastic graduated kind with a sucker, then check the class, they should have the accuracy listed.

Reply 4

Gemmles