Separation Techniques Key Revision Facts

Filtration Filtration will separate insoluble

solids from liquids. The solution is poured through the

equipment to the right The liquid is small enough to pass

through the holes in the filter paper. The solid particles are too big to fit

through the holes so stays at the top. E.g. sand in water – the water passes

through the holes in the filter paper and the sand stays at the top.

Evaporation / Crystallisation A solution of a liquid and a soluble solid is

heated, the liquid evaporates (from a liquid to gas), and solidcrystals are left behind.

e.g. salt water – the water evaporates and the salt is left behind in the evaporating dish. ONLY

the salt is collected.Distillation Distillation can be used to obtain pure water from

salt water. Salt water is heated up until it starts to boil. The

water molecules gain energy and evaporation (from liquid to gas). The water vapour travels down the condenser, it is then cooled and condenses (from gas to liquid). The water is then collected. The salt is left behind in the flask and the water is collected in the flask.

Both the salt AND water are collected using this method.

Chromatography Chromatography can be used to

find out which compounds are in a certain colour of dye or ink.

Method draw a pencil line across the

paper, 1-2 cm from the bottom use a pipette to add small spots of

each ink or dye to the line on the paper

place the paper into a container with a suitable solvent in the bottom

allow the solvent to move through the paper, but remove the chromatogram before it reaches the top

allow the chromatogram to dry, then measure the distance travelled by each spot and by the solvent

Retention factors (Rf)This factor is used to compare chromatograms with different solvent fronts. Calculating the Rf values allows different samples to be compared.

If two substances have the same Rf value, they are not necessarily the same compound. If they have different Rf values, they are definitely different compounds.

Either colour each square Red, Amber or Green or put a tick in each row to indicate how confident you feel with each statement.

I can R A G

I can explain what type of substances filtration can separate.

I can draw and label filtration equipment.

I can give 2 examples when filtration is useful.

I can explain how evaporation can be used to separate mixtures.

I can label a distillation diagram. I can explain how distillation can be used to obtain drinking water from salt water. I can explain how chromatography can be used to separate food colourings or dyes.

Separation Techniques Test Yourself 1

Separation technique namingLabel each of the separation techniques pictured below.

DistillationThe apparatus shows the apparatus to carry out distillation. Number the sentences to explain how distillation works.

True or False?State whether the following statement are true or false.

Chromatography is used by forensic scientists. ___________ When a substance dissolves, it is correct to say it disappears. ___________ A saturated solution will not allow any more solute to dissolve in it. ___________ Filtration will separate a soluble and insoluble substance. ___________ Water is the only solvent. ___________

The water starts to boil and steam is produced.The pure water drips into the conical flask.

1 The salt water is heated.

The steam travels through the condenser.As the steam travels along the condenser it cools down and forms a liquid.

FiltrationUse the following words to label the apparatus: residue, filtrate, insoluble, solid and liquid.

Key Words Word Search

INSOLUBLE SATURATED SOLUBLE

SOLUTE SOLUBILITY SOLUTION

SOLVENTRock SaltRock salt is a mixture of rock and salt. Number the sentences to state how the salt can be separated from the pieces of rock.

Filtration Missing Vowels

r_s_d_ _

f_ltr_t_

_ns_l_bl_

s_l_bl_

l_q_ _d

Problem solvingYou are given a bucket of sandy sea water. Your job is to get as much clean salt as possible from the sandy liquid.

Arrange these sentences in the correct order so they best describe how you would do the experiment.

(i) put the filtrate into an evaporating basin(ii) collect salt from the evaporating basin(iii) filter the sandy mixture(iv) heat the evaporating basin until all the water has gone(v) put filter paper in the filter funnel

Give one safety precaution that you should take when doing your experiment.

_________________________________________________________________

The salt will dissolve.

Pour the salt water into an evaporating dish and heat gently

1 Add warm water to the rock salt and stir.

The water will evaporate and the salt crystals will appear in the evaporating dish.Filter the mixture, the salt solution will collect in the beaker and the pieces of rock will collect in the filter paper.

_________________________________________________________________

Evaporating, filtering and distilling are 3 methods of separating mixtures.Which method would be best to use to

a) get salt from sea water ______________________b) get drinking water from sea water ______________________c) get clean water from muddy water ______________________

Separation Techniques Exam Style Qs

1) Distillation is a method that can be used to obtain drinking water from a sample of salt water. Two different examples of distillation apparatus are shown below.

a) Which apparatus A or B will produce the drinking water the quickest? _______Give a reason for your choice. _________________________________________________________________________________________________________________________________________________________________________________________________________________________

b) Using the following key words, explain how distillation works. Key words: boils, cools, condenses, steam. ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2) Paper chromatography can be used to identify dissolved substances, for example in food colourings. Explain how it works. ____________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

3) In the space below, draw and label the apparatus required to separate a soluble substance from an insoluble substance.

4) A different type of chromatography was used to examine 4 different colours of ink. Compete the table below to show the results.

5) A student used paper chromatography to identify the colours in a black ink.

a) What colours are in the black ink?

____________________________________________________

b) Suggest which colour is least soluble in the solvent. Give a reason for your answer. ________________________________________________________________________________________________________________________________________________

c) Calculate the Rf value for the green colour.

Use the equation: _______________________________________________________________________________________________________________________________________________________________________________________

6) A student used paper chromatography to investigate the colours in different inks. The student made two mistakes in setting up the apparatus.

a) Identify the two mistakes and describe the problem each mistake would cause.Mistake 1 _______________________________________________________ Problem ________________________________________________________ ______________________________________________________________Mistake 2 _______________________________________________________ Problem ________________________________________________________ ______________________________________________________________The student then set up the apparatus without making any mistakes.

b) How can you tell from Figure 2 that the Rf value for the blue ink is greater than the Rf value for the red ink? _______________________________

____________________________________________________________________________________________________________________________

7) The apparatus in the figure below is used to separate a mixture of liquids in a fuel.

a) What is apparatus W on above the figure above? Tick one box.

b) What is the name

of this method of separation? Tick one box.

c) Name the changes of state taking place at A and B in the figure above. Use words from the box.

Change of state at A _____________________

Change of state at B _____________________

 A student measured the melting point of a substance four times.

d)Calculate the mean melting point of the hydrocarbon, leaving out the

anomalous result. Give your answer to two significant figures.________________________________________________________________________________________________________________________________________________________________________

Beaker

Boiling Tube

Flask

JugCrystallisation

Electrolysis

Filtration

Distillation

boiling condensing freezing melting

  Trial 1 Trial 2 Trial 3 Trial 4

Melting point in °C 35 48 37 37

Mean melting point ______________ °C

8) Race horses may be given drugs to improve their perfomance in races. This is illegal in the UK. After races, urine samples are collected from the horses. These samples are tested for drugs. Chromatography is one of the tests used to identify drugs in urine. The diagram shows a chromatogram.

a) How do we know that sample 1 was a pure sample of caffeine? ________ ___________________________

__________________________________________________________

b) Calculate the Rf value for cocaine. Give your answer to 2 significant figures. Use information from the diagram. Use the equation:

__________________________________________________________

__________________________________________________________

Rf value of cocaine = ____________________

c) Give three conclusions about the urine sample from the horse. Use information from the diagram.

1) _____________________________________________________ _____________________________________________________

2) __________________________________________________________________________________________________________

3) __________________________________________________________________________________________________________