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Science Stage 4

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Mixture separation

Part 4 – Separation methods

Number: 43922 Title: Mixture Separation This publication is copyright New South Wales Department of Education and Training (DET), however it may contain material from other sources which is not owned by DET. We would like to acknowledge the following people and organisations whose material has been used: Extract from Science Syllabus Years 7-10 © Board of Studies, NSW 2003 Overview

pp iii-iv

Screenshot of drawing toolbar from Microsoft Word used by permission from Microsoft Corporation.

Part 1, p19

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Copyright Regulations 1969

WARNING This material has been reproduced and communicated to you on behalf of

the New South Wales Department of Education and Training

(Centre for Learning Innovation) pursuant to Part VB of the Copyright Act 1968 (the Act).

The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you

may be the subject of copyright protection under the Act.

All reasonable efforts have been made to obtain copyright permissions. All claims will be settled in good faith. Published by Centre for Learning Innovation (CLI) 51 Wentworth Rd Strathfield NSW 2135 _______________________________________________________________________________________________

_ Copyright of this material is reserved to the Crown in the right of the State of New South Wales. Reproduction or transmittal in whole, or in part, other than in accordance with provisions of the Copyright Act, is prohibited without the written authority of the Centre for Learning Innovation (CLI). © State of New South Wales, Department of Education and Training 2005.

CLI Project Team acknowledgement: Writers: Sue Doolan and Richard Alliband Editors: Julie Haeusler and Rhonda Caddy Illustrators: Quan Pham and Sue Doolan

Contents – Part 4

Lesson 16: Separation using filtration 3 Filtering 6 Evaporating 7

Lesson 17: Combining separation methods 9 Crystallisation as a separation method 13

Lesson 18: Chromatography 15

Lesson 19: Distillation 17

Lesson 20: Flow charts 23

Suggested answers – Part 4 29

Exercises – Part 4 31

Part 4: Separation methods 1

2 Mixture separation

Lesson 16: Separation using filtration

In this lesson, you will make a mixture of flour and Epsom salts, then separate them again. You’ll use the property of these substances called solubility to enable you to separate them. Flour doesn’t dissolve in water, but Epsom salts is soluble in water.

Wash your hands thoroughly at the end of the experiment. Epsom salts is slightly poisonous if you eat it.

Activity: Separating your own mixture

What you will need: • flour

• Epsom salts (If you don’t have Epsom salts, use sugar.)

• plastic teaspoon

• warm water

• heat-resistant jug

• drinking straw

• matches

• filter funnel

• measuring cylinder

• 2 pieces of filter paper

• beaker

• retort ring

• retort stand

• wire gauze

• tripod

• safety goggles

• spirit burner.

You will pass the mixture through a tiny sieve. The sieve has holes so small that you cannot see them. This special sieve is called filter paper and the process of sieving using the paper is called filtering.


What you should do: 1 Put 2 teaspoons of flour and 2 teaspoons of Epsom salts into the jug.

Add 100 mL of warm water. Stir the mixture with the teaspoon. Observe what happens.

a Tick the sentences which describe what you observed.

The flour spread through the water.

The Epsom salts spread through the water.

The flour disappeared.

The Epsom salts disappeared.

The flour sank to the bottom.

The Epsom salts sank to the bottom.

The flour floated.

The Epsom salts floated.

Did you observe that the flour spread through the water but the Epsom salts disappeared?

b Complete this sentence using the names of the substances in the mixture. _____________ forms a solution with water but ____________ forms a suspension with _______________.

The correct sentence is: Epsom salts forms a solution with water but flour forms a suspension with water.

2 Clamp the retort ring to the retort stand.

3 The retort ring supports the filter funnel. Place the filter funnel in the retort ring.

4 Place the beaker under the funnel.

5 Now you need to prepare the filter paper to fit it into the filter funnel. This preparation is called folding the filter paper.

Get at least two pieces of filter paper to practise.


Folding a filter paper Start by folding the filter paper in half.

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Now fold the paper in half again. It is now ¼ of the original size.

first fold

second fold

first fold

fold here again

Hold the paper so that it makes a cone with three thicknesses of paper on one side of the cone.

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6 Moisten the filter paper with some water and place it in the filter funnel.

The filter paper cone should stick to the sides of your filter funnel.

7 Check yourself. Does your equipment look like the following diagram?

(The diagram has been drawn to look more realistic so that it is easy for you to check your equipment. This is not a scientific diagram!)


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Before you begin filtering, here are some problems to avoid!

• You will use a stirring rod to prevent splashes as you pour the mixture into the filter paper. Be careful not to poke a hole in the filter paper with the stirring rod. Stirring rods are usually made from glass, but you will use a drinking straw instead.

• Don’t rush. Filtering is a slow process and you must be patient. Never fill the paper cone more than three-quarters full. If the mixture overflows, it will not pass through the filter paper and will not be separated.

• Make sure you don’t pour any liquid between the funnel and the filter paper.

• Keep the bottom of the funnel against the side of the beaker. This prevents splashing in the beaker.

Filtering 8 To filter the mixture, pour it down the outside length of the drinking

straw into the centre of the filter paper. Remember to pour slowly and don’t overfill the filter paper. Keep the straw away from the paper or you might poke a hole in the filter paper.

9 Add liquid to the filter paper cone until all the mixture is filtered.


Evaporating

Supervisor needed.

Remember to think about safety when you use methylated spirit and when you heat substances. Are you wearing your safety goggles? When the liquid level is low be careful as the hot contents can start to ’spit’ out of the beaker.

10 Take the beaker containing filtered liquid and evaporate the water as shown below:

Go ahead with step 11 while the filtered liquid is being heated but every minute check the equipment. Put out the spirit burner when there are only a few millilitres of liquid left. Leave the equipment to cool while finishing step 12.

11 Look in the filter paper. What do you see?

flour

Epsom salts

12 Imagine that the filter paper is like the sieve drawn below.


This box is the same size as a hole in the sieve.

Your flour ’ball’ must be larger than this box. Your Epsom salts ’ball’ must be smaller than this box.

Draw a ball to represent a piece of flour in water, e.g.

Draw a ball to represent a piece of Epsom salts in water, e.g.

You have used the model of a sieve to predict that the pieces of flour in water are bigger than the pieces of Epsom salts in water.

13 Look in the beaker. What do you see?

flour

Epsom salts

water

Did you see crystals of Epsom salts?

If you can see flour, then there was a problem with your filtering. Look back at the list of problems to avoid in step 7. Decide how to filter better next time.

If you can see water, then you haven’t finished evaporating it. You still have a mixture in your beaker.

Complete Exercise 4.1: Filtering.

What is the difference between a sieve and a filter?

A sieve is usually used to separate mixtures of solid particles that can be seen with the naked eye. The solid particles could be mineral crystals from crushed rock or the solid particles that make up soil. In your kitchen you may have a flour sieve to separate lumps of flour from the fine flour particles.

A filter is usually used to separate mixtures of two states. A filter paper is used to separate solid and liquid while the filter in a vacuum cleaner separates solid dust from the air. Every car has a fuel filter, an air filter and an oil filter designed to trap solid particles. Some water supply collection systems even have animal filters to filter dead animal bodies from the water supply!


Lesson 17: Combining separation methods

Activity: More about filtration

The diagrams below show a filtration experiment.

beaker

filterfunnel

filtrate

residue

retortstand

filter paper

There are two new labels on the equipment. One is the solid that is caught on the filter paper, the other is the liquid that passed through the filter paper.

1 Write down what these words mean:

a residue ________________________________________________ b filtrate ________________________________________________

Residue means the solid part caught on the filter paper. Filtrate means the liquid part that passes through the filter paper.


2 If you separate a mixture of flour and salt by filtration what is the name of the:

a residue ________________________________________________ b filtrate ________________________________________________

Flour was the residue and the solution of salts was the filtrate.

3 Which of these four diagrams is correctly labelled?

filterfunnel

beaker

filtrate

residue

beaker

filterfunnel

residue

filtrate

beaker

filterfunnel

filtrate

residue

filterfunnel

beaker

residue

filtrate

BA

C D

If you answered D, then you can match names with common scientific equipment and you understand the meanings of filtrate and residue.

Ian, Jasmine and Alide were asked to separate a mixture of three parts:

• water

• sand

• salt.

The next activity outlines what they did.


Activity: Three separations

Look at the diagrams that show how the students separated the mixture and then answer the questions.

Ian’s method of separating the mixture

1 What is the name of the process that Ian used?

_________________________________________________________

2 In Ian’s experiment, what was the:

a residue? _______________________________________________ b filtrate? _______________________________________________

beaker 2

beaker 1

Jasmine’s method of separating a mixture


3 What is the name of the process that Jasmine used?

_________________________________________________________

4 What did Jasmine end up with in:

a beaker 1? ______________________________________________ b beaker 2? ______________________________________________

Alide’s method of separating a mixture

5 What is the name of the process that Alide used?

_________________________________________________________

6 What did Alide end up with in the beaker that she heated?

_________________________________________________________

7 Did Alide lose any part of the mixture? Explain your answer.

_________________________________________________________

Check your answers.

Another method of separation is called crystallisation.


Crystallisation as a separation method

Activity: Using crystallisation as a separation method

Monday Tuesday WednesdaySunday

Crystallisation of copper sulfate from solution

What substances would you mix to make a copper sulfate solution?

_____________________________________________________________

The solution would contain copper sulfate (as the solute) and water (as the solvent).

From Sunday to Wednesday, the volume of solution decreases (gets less). What are two other changes that occur?

_____________________________________________________________

_____________________________________________________________

The colour of the solution became paler and that crystals formed and gradually grew larger.

The solution loses its colour because dissolved copper sulfate comes out of the solution and adds onto the crystals. That is why the crystals grow. The growth of crystals is called crystallisation.

Complete Exercise 4.2: Planning a filtration.


Lesson 18: Chromatography

Chromatography separates substances by using differences in their ability to move through another substance.

Activity: Chromatography

What you will need:

• 2 pieces of filter paper

• clock glass

• 2 different coloured or different types of water-soluble pens or pencils

• eye dropper, or a tap that will drip.

What you should do: 1 Use one water-soluble pen to draw a dark spot about as big as this ball

in the middle of one piece of filter paper.

2 Place the filter paper in the middle of the clock glass. The edges of the paper will touch the clock glass but the middle with the spot you’ve drawn won’t touch.

3 Place one or two drops of water directly onto the spot. Then wait and watch. When there are no more changes, take the filter paper off the clock glass and set it aside to dry.

4 Repeat the process with your other coloured pen and piece of filter paper.

You should be able to see coloured circles on each piece of filter paper.

What you can see will help you understand the name, chromatography. Chromato means colour and ’gram’ is a Greek word that can mean line. When people first saw these patterns they called them coloured lines, or chromatograms.

Making chromatograms is called chromatography.

Label your chromatograms because you will include one with the send-in page for this lesson. On the dry paper print your name, the date of the chromatogram and the material used. Label any lines/colours.


Why does it work?

Here is a labelled photograph of Chantelle’s chromatogram.

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Which coloured ink moved the most in Chantelle’s experiment?

_____________________________________________________________

Pale blue ink moves the furthest from the spot.

Pale blue ink moved through the filter paper more easily that purple ink. The black ink hardly moved at all. The three colours of ink have been separated using their ability to move through the filter paper.

Paper is not the only substance that can be used to separate mixtures. Columns of chalk, jelly and liquids are also used in chromatography. Chromatography is especially important for separating mixtures from inside living things.

Complete Exercise 4.3: Chromatography.


Lesson 19: Distillation

When you evaporate a solution made from salt and water, the salt remains but the water is lost. In many parts of the world, the water would be the part of the mixture that you wanted to keep. Many people need to make salty water pure so that they can survive. Pure water is needed for drinking and growing crops.

Distillation is the name of a separation method that collects pure liquid from solutions or mixtures of liquids. In this activity, you are going to carry out a simple distillation.

Your supervisor will need to be present for this practical task.

Please clean your equipment thoroughly before you start the experiment. You will use a taste test to find out whether you have separated the mixture.

Your send-in exercise for this lesson will be a report about the experiment. Look at the send-in exercise before you start. As you do the experiment, tick the correct observations in the list and number the observations.

Activity: Distillation

What you will need:

• beaker

• clock glass

• tripod

• wire gauze

• safety goggles

• spirit burner

• matches

• hot water

• table salt

• cup or mug

• plastic teaspoon.


Make sure you are wearing your safety goggles.

What you should do: 1 Using the beaker, get 50 mL of hot water from your kitchen.

Put 3 teaspoons of salt in the hot water. Stir the mixture until the salt dissolves.

2 Put the beaker on your tripod (with the gauze in place) and heat the water.

3 When the water starts to boil, hold the clock glass in the steam coming off the water.

The diagram below will help you to place the clock glass correctly. Use your test tube holder if the clock glass gets too hot to hold with your fingers.

cup

clock glass

beaker

gauze

tripod

spirit burner

Equipment set up

4 When you have collected some water in the cup, stop heating the water. Now taste the water in the cup. Would you describe the water as pure or salty?

Tick the correct observations in the list. You should also number the observations as you make them so that they are in order.


Possible observations Tick if observed

Order of observation

The liquid water changed into a gas.

Bubbles formed in the water as it was heated.

Water formed crystals in the cup.

The salt stayed in the beaker.

The experiment made pure water from salty water.

The water in the cup was pure water.

The water turned cloudy as it was heated.

The water cooled on the clock glass and formed a liquid again.

Salt condensed on the clock glass.

The experiment made salty water from pure water.

There was no salt left in the beaker.

There are six correct statements in the list, so make sure that you have ticked six statements.

A student called Cuz also wants to distil salt water, but in another way.

Activity: Another distillation of salt water

Here is a diagram of the equipment that Cuz used to distil salty water. (Cuz hasn’t put all the labels on his diagram yet.)

salty water

glass tubing

water bath

250 mL beaker

test tube

1 Would you put hot or cold water in the water bath? Explain your answer.

_________________________________________________________

_________________________________________________________


The water bath should contain cold water, because cold water will cool down the steam better. Then the steam will condense to water.

2 What would you expect to find in the test tube?

_________________________________________________________

The test tube should contain pure water.

3 Do you think this equipment is more efficient than the equipment you used? Explain your answer.

_________________________________________________________

_________________________________________________________

The equipment is more efficient because less steam is lost. More water can be collected.

Imagination can produce a creative solution to a problem

Activity: Emergency equipment

Many ships carry equipment to distil pure water from sea water. In the 1973 Round the World Yacht Race, one yacht lost its drinking water from a leaking tank. The crew of the yacht showed imagination and came up with a creative solution to the problem. They rigged up this apparatus to make fresh water.

rubber tubing

sea water

plastic bottle

pressurecooker

steam leaves thepressure cooker

dish containingsea water

purecollectedwater

Compare this equipment with Cuz’s equipment. Which part of the crew’s apparatus has the same function or job as the:

a conical flask with the salty water? ______________________________

b spirit burner? ______________________________________________

c glass tubing? ______________________________________________

d water bath? ________________________________________________

e test tube? _________________________________________________


Check your answers.

The parts of distillation apparatus have special names. These are listed in the table below.

Apparatus Description

distillation flask place where the mixture is placed

condenser place where the gas is changed into a liquid, or condensed

delivery tube tube where the condensed liquid passes

collecting vessel place where the pure liquid is collected

Activity: Distillation apparatus

1 Label the diagram of the yacht’s distillation equipment using the names: distillation flask, condenser, delivery tube and collecting vessel.

Check your labels.

Look carefully at the photograph of distillation apparatus in a laboratory on the next page and then answer the questions.

2 There are no labels on the photograph. Use the special names of the parts of distillation apparatus (from the previous page) to label the equipment.

3 The photograph shows the distillation of a solution. The solute is a blue substance called copper sulfate. Which part or parts of the equipment will contain the blue substance at the end of the distillation?

_________________________________________________________


Check your answers.

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4 Name the part of the distillation apparatus where:

a) evaporation occurs ______________________________________ b) condensation occurs. ____________________________________

Check your answer.

Complete Exercise 4.4: Distillation of salt water.


Lesson 20: Flow charts

A flow chart is a diagram that shows the steps in a process. It can make a complicated process look simple by breaking it into small steps and showing the order of the steps. The steps are connected by arrows. Sometimes a flow chart is a simple series, but some flow charts have return loops.

One example of a simple flow chart is a food chain.

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A food chain

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To interpret the flow chart in the next activity, start reading at the first box and then follow the arrows to the other boxes.

Activity: Flow charts

1 What does this flow chart about a separation show you? Write out the information from the flow chart in your own words.

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_________________________________________________________

_________________________________________________________

The flow chart tells you that if you place a mixture of flour and water in a container and spin it, the flour sinks to the bottom and the water can be poured off (decanted).


Activity: Water treatment diagram and flow chart

Below is a diagram outlining one method of water treatment.

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Treatment of drinking water

The flow chart below was made from the diagram.

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Flow chart of how drinking water is treated

1 What is the first step in the process?

_________________________________________________________

In the first step, water comes from the reservoir.

2 What are the two steps where chemicals are added?

_________________________________________________________


Chemicals are added at the coagulation step and the chlorination step.

3 Which step comes before coagulation?

_________________________________________________________

Sedimentation comes before coagulation.

4 What happens during sedimentation?

_________________________________________________________

In sedimentation, large particles settle out of the water.

5 Why is the water aerated?

_________________________________________________________

The water is aerated to make it taste better.

Lets look at another example.

Activity: Distillation of crude oil flow chart

Use the flow chart to answer the questions following.

This flow chart shows how crude oil is distilled to give useful products. Don’t be concerned by new words you don’t understand.

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Distillation of crude oil


1 How many groups of products are produced by distillation in the fractionating column?

_________________________________________________________

2 How many parts is the fuel oil group split into?

_________________________________________________________

3 What is the name of the process used to separate lubricating oil from bitumen?

_________________________________________________________

4 What is fed into the catalytic cracker? What is formed?

_________________________________________________________

Check your answers.

Activity: Coal fired power station flow chart

The next flow chart shows how our electricity is generated in a coal-burning power station. This flow chart has a return loop.

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How a coal-fired power station works


1 Which substances are added to the system?

_________________________________________________________

2 What happens to the coal?

_________________________________________________________

3 Which substance is returned to another part of the system?

_________________________________________________________

4 What must happen before the generator can produce electricity?

_________________________________________________________

Check your answers.

Complete Exercise 4.5: Mixture separation flow chart.


Suggested answers – Part 4

Activity: Three separations 1 The process is filtration because Ian filtered the mixture.

2 a sand

b salty water (salt solution) 3 The process is decantation because Jasmine decanted the mixture.

4 a sand

b salty water (salt solution) 5 The process is evaporation because Alide evaporated water from the

mixture.

6 The beaker will contain a mixture of sand and salt.

7 Alide lost the water when she evaporated the mixture.

Activity: Emergency equipment a pressure cooker (with sea water)

b gas ring

c rubber tubing

d dish containing cold sea water

e plastic bottle

Activity: Distillation apparatus

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3 The blue substance will be in the distillation flask.

4a Evaporation occurs in the distillation flask.

4b Condensation occurs in the condenser.

Activity: Distillation of crude oil flow chart 1 Five groups of products are produced.

2 The fuel oil group is split into three parts.

3 Vacuum distillation is used to separate lubricating oil from bitumen.

4 Diesel oil is fed into the catalytic cracker. Petrol is formed.

Activity: Coal fired power station flow chart 1 Coal and air are added to the system.

2 The coal is burned in air.

3 Steam is returned to the system.

4 The turbine must be driven by steam.


Exercises – Part 4

Exercises 4.1 to 4.5

Name ________________________________________________________

Teacher ______________________________________________________

Exercise 4.1: Filtering 1 Here is a photograph of a student filtering a mixture of copper sulfate,

copper oxide and water. What is the student doing wrong?

_________________________________________________________

_________________________________________________________


2 The student noticed that copper oxide stayed in the filter paper but the solution of copper sulfate dripped down into the conical flask.

Use the ball and sieve model to explain what is happening.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

3 In the space below, draw a scientific diagram of the equipment you used to filter the mixture of flour and Epsom salts. Make sure that you use the equipment code for every piece of equipment.

Label your diagram.


Exercise 4.2: Planning a filtration

Imagine that you have been given a mixture of sugar, sand and water.

1 Outline what you would do to get a pure dry sample of sugar from the mixture. Write your plan as clearly as possible by setting out the steps you would carry out in order.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

2 Is this the only way that you could separate these substances? Why or why not?

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________


Exercise 4.3: Chromatography

Glue your clearest chromatogram in the space below. (Make sure it is dry first.)

Label the colour that has the greatest ability to move through filter paper.


Exercise 4.4: Distillation of salt water 1 During your lesson, you distilled salty water. Copy your observations in

the order you made them. The first observation has been filled in for you.

1 Bubbles formed in the water as it was heated.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

2 Many large Australian cities are experiencing water shortages. One suggestion for Adelaide has been to tow icebergs, made up of fresh water, from near Antarctica.

Can you use your imagination to come up with a creative solution to another Australian city water shortage?

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________


Exercise 4.5: Mixture separation flow chart 1 This flow chart starts with a mixture that contains five different

substances. One of the substances is water. The other four substances are mixed with the water. One of them is dissolved. The letters A, B, C, D and E stand for the substances and water.

The flow chart shows how the mixture was separated into its five parts (four substances and water).

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Use the flow chart to answer these questions.

a) Which substance in the flow chart could be iron filings (A, B, C, D or E)?

______________________________________________________

b) Which substance, B or C, has the larger particles?

______________________________________________________

c) Which substance in the flow chart is water (A, B, C, D, or E) ?

______________________________________________________


d) Name one substance, from the flow chart, that is insoluble in water (A, B, C, D, or E).

______________________________________________________

e) A substance called sodium sulfate is not attracted to a magnet and dissolves in water. Which substance in the flow chart could be sodium sulfate (A, B, C, D, or E)?

______________________________________________________

2 Look back at the water treatment diagram and flow chart. Select two technologies that make a task easier or more convenient.

Identify (recognise and name) each technology and describe how they would make providing clean water easier or more convenient.

a) ______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

b) ______________________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________


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