LO: to explain how we can separate different solvents

from a solutionChromatography

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.

Discuss with your partner and then write down a step by step guide to help Johnny

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.

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

What you will needSkittles and M&Ms: two each of the same colour 2 x watch glass pipettechromatography paper 10ml beaker

 

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. ThiefWe know that it must have been someone in

science. When we checked we found four science teachers who had green felt tip pens.

Who stole Mr Grace’s mug?

Discuss with your partner, then write a paragraph to explain how you would find out who took Ms Lee’s mug

The suspect ink which has the same chromatograph (pattern of coloured dyes) as the killer’s fountain pen is guilty.

If C is the killers fountain pen, which suspect is guilty?

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 penSamples A, B and C are the samples taken from the homes

of the suspects. How can we find the killer?

Plenary- discuss with your partner

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 informationSpinach, 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.

Name the compound formed from these elements

nitrogenlithium

sulphurzinc

iodinenickel

brominealuminium

oxygentin

chlorinesodium

nitrogenmagnesium

sulphuriron

Name of compoundElement 2Element 1

iron sulphide

magnesium nitride

sodium chloride

tin oxide

aluminium bromide

nickel iodide

zinc sulphide

lithium nitride

Naming Simple compounds.

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 Boiling water to make tea. •  2 Dissolving sugar in a cup of tea. •  3 Melting snow. •  4 Making crisps from cooking oil and

potatoes. •  5 Lighting a match. •  6 Freezing water to make ice. •  7 An apple ripening. •  8 Cutting up a pear. •  9 Digesting a banana. • 10 A forest fire.