Chromatography
LO: to explain how we can
separate different solvents
from a solution
Discuss with your partner and then write down a
step by step guide to help Johnny
Little Johnny is at it again! While I was looking
after little Johnny he poured salt into his
mums favourite plant! He got his spoon and
mixed it in really well. If I leave it there it will
kill the plant. Help! How can I get the salt out
quickly before his mum comes back?
Use the following words in helping to tell me
how to get the salt out.
Filter,
dissolve,
solution,
filter paper,
water.
Chromatography
• Inks can be separated into the different dyes that they are
made up of by a process known as chromatography.
• The solvent soaks through the paper carrying the ink with
it.
• The more soluble dyes (particles) travel the fastest on the
paper.
• The less soluble dyes (particles) travel slower on the
paper.
What you will need
Skittles and M&Ms: two each of the same colour
chromatography paper
10ml beaker
2 x watch glass
pipette
METHOD
1 Make two pencil dots equally spaced along the line and mark one ‘S’ for
Smarties and the other ‘M’ for M&Ms.
2 Take two skittles of the same colour and place them on the watch glass. Add
one or two drops of water on top and swill it around to wash the colour off
the Skittles into the water.
3 Take a pipette and transfer a drop of the coloured water on to the filter paper
4. If the colour looks a bit weak, let the drop dry and repeat with a second drop.
If necessary, repeat again.
5. Repeat steps with two M&Ms of the same colour as the Skittles. Put the
drop(s) on the second spot on your paper.
6. Suspend your paper in a beaker with water in the bottom. Make sure the
water reaches the bottom of the paper but not the coloured spots.
7 Leave the chromatogram to develop and see if there are any common food
dyes present
8 Repeat with different colours
Who stole Mr Grace’s mug?
Mr Grace went to have a coffee and couldn’t find his mug.
While he was looking for it he found this note.
Ms. Lee
If you ever want to see your mug again you need
to bring 100,000rmb to the school hall at
midnight tonight.
A. Thief
We know that it must have been someone in
science. When we checked we found four science
teachers who had green felt tip pens.
Discuss with your partner, then write a paragraph to explain
how you would find out who took Ms Lee’s mug
If C is the killers fountain pen, which
suspect is guilty?
The suspect ink
which has the same
chromatograph
(pattern of coloured
dyes) as the killer’s
fountain pen is
guilty.
Plenary- discuss with your partner
Catch the killer!
A man has been found murdered by the side of a road.
Police have arrested three suspects but have very
few clues. During the struggle, the killer dropped a
fountain pen. When the police searched the homes
of the three suspects they found that each had a
bottle of ink.
Sample evidence is the ink from the fountain pen
Samples A, B and C are the samples taken from the homes
of the suspects.
How can we find the killer?
Smartie chromatography
• Why are smarties different colours?
• Are they pure or a mixture? What
investigation could you do to answer this
question
Questions
1.
Why do some dyes separate into different colours
yet others do not?
2.
Why do some dyes move further up the
chromatography paper than others?
Leaf chromatography
• Vanish on leaves
A witness saw a burglar jump out of a window and land
in a patch of nettles. Later, police arrest a man with
green marks on his T-shirt. The suspect claims that
some of the marks are grass stains. He got them when
playing football. He says that the others are from
spinach spilt when eating dinner.
You will use chromatography to try to find out whether
the suspect is telling the truth or whether he’s likely to be
the burglar.
Useful information
Spinach, nettle and grass
leaves contain a mixture of
green, yellow and orange
pigments. The mixture in
each type of leaf is different.
So each leaf makes a
different chromatogram.
Naming Simple compounds.
Name the compound formed from these elements
Element 1
Element 2 Name of compound
iron
magnesium
sodium
tin
aluminium
nickel
zinc
lithium
sulphur
nitrogen
chlorine
oxygen
bromine
iodine
sulphur
nitrogen
iron sulphide
magnesium nitride
sodium chloride
tin oxide
aluminium bromide
nickel iodide
zinc sulphide
lithium nitride
Can you remember the three lab methods for separating
mixtures?
filtering
chromatography
distillation
Which of these does each method do?
A separates a solvent from a solution
B separates a solid from a liquid
C separates substances with different solubility's
• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10
Boiling water to make tea.
Dissolving sugar in a cup of tea.
Melting snow.
Making crisps from cooking oil and potatoes.
Lighting a match.
Freezing water to make ice.
An apple ripening.
Cutting up a pear.
Digesting a banana.
A forest fire.