Experiment - Chromatography
Simple Chromatography Experiment
You will need:
Some blotting paper (~£1.75)
Some disposal plastic cups 1.5 cups per Beaver
Some water soluble coloured felt tips (yellow red + a dark colour)
Some straws for using a pipette - optional
Some large jugs of water - to fill up cups
Preparation ~1hr the night before cut the blotting paper in to strips 1.5 cm wide and approx twice as high as your cups
Setting up Activity ~15 mins
Leave for 20 - 30 mins
Talk after to go over what we discovered
For each strip place a small yellow dot in the middle about about 2 cm from bottom edge.
Place a small red dot over the yellow dot.
Place another dark colour over red dot
(the dot should now "look" black).
One cup per beaver mark a line 2cm from bottom - this will be the fill mark
The other cups are filled up with water and Beavers pour water from this cup into their cup.
Explain we are going to suspend the paper just in the water.
Ask the Beavers what they think will happen.
What happens when the paper touches the water.
When the water moves, what, if anything happens to the dot?
The key points are:
- Water travels up the paper by "capillary" action
- Water takes the soluble ink molecules with it.
- The bigger the molecules the slower they travel
- Controls ballpoint , pencil. no soluble in water
Using a ball point pen, add initials to side opposite from dot.
Full up cup to level mark ~2 cmd
Place end of paper ~1 cm in water with a ~1cm gap before dot.
Fold paper over edge, so paper stays in place.
Note the experiment will not work if:
The water goes over the dot.
The water does no touch the dot.
Once folded in place leave for ~20 mins to allow colours to separate.
Epilogue - if required ...
Look and nice pattern
Why do the colours separate?
Why did the ballpoint pen / pencil not separate?
Which are the bigger molecules (the are the ones that travel the least distance)
Are there any practical uses for this technique can be use to separate complex, big molecules from little molecules
It is often used in chemistry biology for identify complex substances.
Using a very similar method scientist have discovered
- we share 96 percent of our DNA chimpanzees - our closes animal relative
- we share ~50% of our DNA with Banana and Cabbages
- all humans share 99% of the DNA
This kind of method can help identify what things are made from and where they come from.
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- Experiment - Explain
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- Experiment - Predict