1. Methods of Separating Mixtures
Magnet
Filter
Settling
Decant
Evaporation
Chromatography
Distillation

2. Separating mixtures
If we add 10g of salt to 50g of seawater, how much would the mixture weigh?
How much salt would be recovered if we separated this mixture by evaporation?

3. Magnets What types of materials will magnets attract?
Magnets will attract IRON, STEEL (NICKEL and COBALT as well).
How could you separate a mixture of sulphur and iron filings?
By using a MAGNET!
Separating iron and sulphur
1. mixture of iron and sulphur and a magnet.
2. Wrap the magnet in a paper-towel.
3. Use the magnet to separate the iron filings from the sulphur.
Questions
1. What did you observe?
2. Could you use a magnet to separate gold and sulphur?
The iron filings are attracted to the magnet.
No, gold is not magnetic.

4. Settling Separating sand and water 1. Fill a beaker with water.
2. Add some sand to the water.
3. Stir the sand using a glass rod. What do you observe?
4. Wait a couple of minutes. What can you see now?
What happened?
The sand particles are pulled to the base of the beaker by GRAVITY.
Extension activity
Repeat the experiment above but instead of just sand use a mixture of sand and gravel. What do you observe?

5. Decanting Separating sand and water
1. Take a beaker containing water with sand settled at the bottom.
2. Carefully pour away the water whilst trying not to disturb the sand.
3. How clean is the water you have poured off (decanted)?
Is there a better method of separating sand and water?
It is very difficult using the decanting method to obtain pure water that contains no sand particles. There is a better way of separating sand and water, we will look at that next.

6. Filtration

7. Filtration separates a liquid from a solid
Mixture of
solid and
liquid
Stirring
rod
Filtrate (liquid
component
of the mixture)
Filter paper
traps solid
Funnel
Filtration separates a liquid from a solid

9. Separating Mixtures

10. Exercise 1: Filtrate and Residue
1. Which substance was left on the filter paper (this is called the RESIDUE)?
2. Which substance passed through the filter paper (this is called the FILTRATE)?
3. Could you use the filtration method to separate salt and water?
The sand was the residue.
Water was the filtrate.
No, salt is soluble in water and would therefore pass through the filter paper with the water.
Filtrate

12. Paper Chromatography

13. Chromatography Tie-dye t-shirt Black pen ink DNA testing Crime scene
Paternity testing

14. Chromatography
1. Take a piece of filter paper and draw a large dot in the middle with a coloured felt-tip pen.
2. Then using a dropper add a couple of drops of water onto the ink dot.
3. Note your observations.
What did you observe?
The ink drop separates out into its component colours. The pattern you get depends upon the colour of felt-tip pen you use.

15. Exercise 5: Chromatography
1. Four coloured felt-tip pens produce the ink patterns below.
a) Which ink dot contains only one colour?
b) Which ink dot contains three colours?
c) Which two ink dots contain two colours? A D
B & C

16. Evaporation
When wet clothes are left on a washing line they eventually become dry. Why?
The water on the clothes evaporates (changes from a liquid into a gas).
How could you use a similar method to separate salt and water?
If you heat a solution of salt and water and then leave it for a few days the water will EVAPORATE and leave the salt behind.
Separating salt and water
1. Your teacher will give you a solution of salt and water.
2. Set up the apparatus as shown on the right.
3. Pour some of the solution into the evaporation dish.
4. Place the evaporation dish onto the gauze.
5. Heat the solution for 30 seconds using a blue Bunsen flame.
6. Let the evaporation dish cool and then leave in a safe place for a few days.
7. After a few days note down your observations.

17. Setup to heat a solution
Ring stand
Beaker
Wire gauze
Ring
Bunsen burner

18. Separating Mixtures

19. Distillation Separating salt and water
1. Your teacher will give you a solution of salt and water.
2. Set up the apparatus as shown below.
Leibig Condenser
3. Add some of the solution into the flask.
Delivery tube
4. Fit the delivery tube and bung into the conical flask.
5. Heat the solution using a blue Bunsen flame.
6. Note your observations.
Bung
Distillate

20. A Distillation Apparatus
liquid with a solid
dissolved in it
thermometer
condenser
tube
distilling
flask
pure
liquid
receiving
hose connected to
cold water faucet
“A Distillation Apparatus”
Description: This transparency shows an apparatus used for laboratory distillations.
Basic Concepts
The separation of substances by distillation occurs because the boiling point of the substances differ. The substance with the lowest boiling point boils away first.
Distillation is based on the principle that a substance will change from a liquid to a vapor during heating and from a vapor back to a liquid while cooling.
Teaching Strategies
Use this slide to explain to students how a distillation apparatus is used to purify liquids and to separate the components of liquid mixtures. Begin by reviewing the phases of matter, stressing the processes of evaporation and condensation. Remind students that different liquids have different boiling points. Point out that substances that are solids at room temperature usually have higher boiling points than do substances that are liquids at room temperature.
Questions
If the distilling flask shown in the diagram were open to the air (rather than being connected to the condensor), what would happen to each component of the mixture in the flask as boiling continued?
Explain your answer to question 1 in terms of the boiling points of the liquid and the dissolved solid.
In the distillation apparatus, the vaporized liquid must enter the condenser. The condenser consists of a long tube within another tube (the jacket). The substance in the central tube and the jacket cannot mix. Cold water enters at the bottom of the jacket and exits at the top.
What is the function of the condenser jacket?
How would changing the length of the condenser jacket affect how well it performs this function?
Explain why the liquid entering the receiving flask is pure.
To separate a mixture of methanol and water, you set up a distillation apparatus and heat the mixture to the boiling point of methanol, 65 oC.
What substance would you expect to collect at the receiving flask?
When you finish the experiment, you discover that the substance in the receiving flask is not pure. It still contains both water and methanol. Can you explain why? (Hint: Think about vapor pressures.)
Before automobiles were invented, crude petroleum was used mainly as a source of kerosene. The petroleum was heated in a device called a still. Gasoline, then considered to be useless, evaporated first into the air. Kerosene boiled off next and was condensed and collected. A tar-like residue remained in the still. From this information, what can you deduce about the boiling points of gasoline, kerosene, and the residue?
How will you know when all of one component has been separated?

21. The solution is boiled and steam is driven off.

22. Salt remains after all water is boiled off.

23. No chemical change occurs when salt water is distilled.
Saltwater solution
(homogeneous mixture)
Distillation
(physical method)
Salt
Pure water

24. Separation of a sand-saltwater mixture.

25. Separation of Sand from Salt
Gently break up your salt-crusted sand with a plastic spoon.
Follow this flowchart to make a complete separation.
Salt-
crusted
sand.
Weigh the
mixture.
Pour into
heat-resistant
container.
Fill with
water.
Stir and let
settle 1
minute.
Dry
sand.
Calculate
weight of
salt.
Weigh
sand.
Decant
clear
liquid. No
How does this flow
chart insure a complete
separation?
Wet
sand.
Evaporate to
dryness.
Repeat
3 times?
Yes

26. Separating mixtures
How would you get salt from seawater?
Evaporate the water and the salt is left behind.
This is exactly how the salt that can be found on the ground (or under it) was formed.
Seas that evaporated MILLIONS of years ago, left the salt behind.

27. Exercise 6: Link the Separation Techniques
Chromatography
Iron and sulphur
Evaporation
Sand and water
Distillation
Ink from water
Filtration
Salt from water
Colours in brown ink
Magnet