Chemical
Science
7.2 Chemical Science
Dec 2014
1
AUSTRALIAN CURRICULUM
Chemical sciences
Mixtures, including solutions, contain a combination of pure substances that can be separated using a
range of techniques:

recognising the differences between pure substances and mixtures and identifying examples of
each

identifying the solvent and solute in solutions

investigating and using a range of physical separation techniques such as filtration, decantation,
evaporation, crystallisation, chromatography and distillation

exploring and comparing separation methods used in the home
Science as a Human Endeavour
People use understanding and skills from across the disciplines of science in their occupations:

recognising that water management plays a role in areas such as farming, land management and
gardening

investigating how separation techniques are used in the food and wine industries

considering how seasonal changes affect people in a variety of activities such as farming

considering how sports scientists apply knowledge of forces in order to improve performance
2
CHEMICAL SCIENCE
CONTENTS PAGE
Activity
Page
1
What is chemistry?
4
2
Matter for a Chemist
5
3
Pure Substances and Mixtures
7
4
Mixture of solution
9
5
Solubility
10
6
Sedimentation & Decantation
13
7
Filtration
14
8
Centrifugation
16
9
Evaporation
18
Distillation
19
Library Assignment – Separating in the real world
22
Chromatography
23
Investigation 1: Chromatography
24
Crystallisation
25
Summary of separation processes
28
Investigation 2: Investigating soft drink
29
10
11
12
3
Activity 1: What is chemistry?
CHEMISTRY ~ this is a word that you have heard before.
What does it mean to you?
Why is chemistry called a science?
What do you think a chemist does?
What would you like to find out about chemistry?
Join with the members of your group to bounce around some ideas to answer each of
these questions.
Decide who in your group will act as a recorder. This person should list your
group’s ideas on a piece of paper.
Share your group’s ideas with your class and then write down answers to each
question in your notebook.
Chemistry is ..........
Chemistry is a science because ...................
If I were a chemist my working day would be spent ...................
In studying chemistry I would like
to find out how .....................
4
Activity 2: Matter for a Chemist
We are surrounded by the material that interests the chemist……we breathe it, we
swim in it, we eat it, we make objects from it and we ourselves are made from it. This
marvellous stuff is called MATTER.
Our Universe is thought to consist of matter of various kinds. What is special about
matter is that it takes up space and has mass. The matter of our world is present in
three main forms - solids, liquids and gases.
Let us begin our study of chemistry by investigating the different forms of matter.
AIM:
To compare the properties of the three states of matter.
MATERIALS:
Samples of:






wood
kerosene
test tube of nitrogen
iron
sulfur powder
moist clay






glass
lead shot in a sealed vial
limestone
oil
test tube of oxygen
honey


test tube
Bunsen burner & matches
For teacher demonstration:


large syringe
iodine crystals
1.
Examine each of the materials listed above.
2.
Copy the following table into your notebook. Classify each of the materials
under the headings as being solids, liquids or gases.
SOLIDS
LIQUIDS
GASES
3.
Was there any substance that was difficult to classify? If so, explain why this
substance was a problem for you.
4.
How did you decide whether a substance was a solid, liquid or a gas?
5
Physical Properties of Each State
Each of the three states of matter has its own special properties.
Your teacher will demonstrate what is meant by compressibility using the syringe
filled with air then with water.
 The ability of a gas to be poured can be tested by heating two or three crystals of
iodine in a test tube. Your teacher should do this since iodine is poisonous.

5.
Copy and complete the following table of properties into your notebook. Then
examine the samples and answer ‘yes’ or ‘no’ in the spaces to complete it.
PROPERTY
SOLIDS
LIQUIDS
GASES
Do they keep their own rigid shape?
Do they take up the shape of the container?
Can they be poured?
Does the top surface always stay level?
Do they spread out to fill the container?
Can they be compressed?
Do they always flow to the lowest part of
the container
6.
Use this table to make your own summary list of the properties of the three
states of matter.
A Strange Liquid?……..Solid?…….Liquid?…..?
?
Try this one at home …….
In a bowl, mix half a cup of corn flour with some water to make thick dough. Add
one or two drops of food colouring if you wish. When the dough is mixed well it will
not be sticky. Now see what happens to this dough when you let it ‘run’ through
your fingers. Knead the dough some more.
What do you notice about this strange mixture?
6
Activity 3: Pure Substances and Mixtures
Mixtures are all around us, and most of
the things you can touch or feel are
mixtures, not pure substances.
A lot of times this isn’t a problem.
Orange juice is a mixture of water,
sugar, vitamin C, citric acid, and more,
and it’s perfectly fine as a mixture. But sometimes we need to separate the different
substances in a mixture.
For example, milk is a mixture of water, sugar, fat, protein, vitamins, calcium, and
more. Calcium and protein are two things your body needs, but fat, while good for
growing children, can be unhealthy for adults. To make healthier milk for adults,
we separate most of the fat from the milk, creating low-fat or “skim” milk.
Six of the possible kinds of mixtures are:
a) a mixture of gases
b) a mixture of liquids
c) a mixture of solids
d) a mixture of gases in a liquid
e) a mixture of solids in a liquid
f) a mixture of solids and gases
In each of the following pictures there is an arrow that points to a type of mixture
listed above. Match the type of mixture to each picture.
7
QUESTIONS: True or false?
8
Activity 4: Mixture or solution?
A mixture is when two or more substances are mixed
together and there is no chemical change. Mixtures can
usually be separated back to the original components using a
variety of techniques.
Examples of mixtures include sand and water, a mixed salad, salt water, a bag of
assorted nails etc. The composition of a mixture can be varied by changing the
proportion of the substances that make it up.
Solutions are also mixtures. A solution is a type of mixture where one substance is
dissolved in the other. In solutions the substance that dissolves will, over time,
become evenly distributed throughout. E.g a solution of sugar and water means the
sugar is evenly distributed throughout the water.
If we compare sugar and water to sand and water - both are a type of mixture. The
sugar dissolves and is evenly dispersed throughout the water while the sand sinks to
the bottom. The sugar and water mixture is a solution while the sand and water
mixture is not a solution.
Solutions can also be gases dissolved in a liquid such as carbonated water found in
fizzy drinks. In this case, the carbon dioxide (CO2) is evenly distributed throughout
the water, making it a solution. The bubbles that we see in fizzy drinks are not part
of the solution; rather they are the carbon dioxide that has separated from the
solution and been released as gas.
QUESTIONS:
1. What is a mixture?
2. What is a solution?
3. What are some of the ways mixtures can be separated?
4. Why might a mixture need to be separated?
5. What do you understand by the terms reversible and irreversible changes? Give
some examples to support your thinking.
9
Activity 5: Solubility
Compounds differ in their ability to dissolve in water. Those that dissolve easily are
said to be soluble, those that do not dissolve easily are said to be sparingly soluble,
while those that do not appear to dissolve at all are said to be insoluble. A solution
can have a colour, but unless you tried to dissolve too much solid, it will appear
clear.
AIM:
To classify a range of substances for their solubility in water.
MATERIALS:
Small samples of:
 sand
 copper sulfate
 chalk powder
 copper carbonate
 sodium chloride
 sugar
and:
 popsticks
 250 mL beaker of water
 test tubes and stoppers (6)
 test tube rack
PROCEDURE:
In your group
1. Predict which of the substances will be the most soluble and which will be the
least soluble. Write down your predictions.
2. Discuss with your group members how you might best test the sample
substances listed above for their ability to dissolve in water.
Consider
a. How will you carry out the test?
b. Which variables will you have to control?
c. How will you control these variables?
d. How will you present your results?
3. Check your group's procedure with your teacher.
4. Test your predictions.
5. In your notebook, under the heading ‘Results’, record your findings in a
suitable table.
10
SUMMARY:
In carrying out this investigation you used water as the substance to dissolve
the solid.



The substance that does the dissolving is called the solvent.
The substance that is dissolved is called the solute.
The resulting mixture is known as the solution.
6. Write a word equation that shows the parts involved in forming a solution.
7. Identify the solute, solvent and solution in the mixture given below. Write a
word equation that shows the parts involved in forming a solution.
How can you remember the difference between a
solute and…..
a solvvvvvvvvvvvv
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vent???
Separating Substances
Mixing different materials together has helped chemists find
out many interesting facts about the chemical world.
Chemists also need to be able to separate mixtures of
substances, so they can investigate the properties of each
different part. The choice of method depends on what is to be
separated.
In the following activities you will learn how to use each of these methods:
Part A: Separating Insoluble Substances from a Liquid
A. Sedimentation
B. Decantation
C. Filtration
D. Centrifugation
Part B: Separating a Solute from a Solvent
E. Chromatography
F. Evaporation
G. Distillation
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Part A: Separating Insoluble Substances From A Liquid
Activity 6: Sedimentation & Decantation
An insoluble substance mixed into a liquid normally settles to the bottom of the
container. The liquid can then be poured from the top leaving the undissolved
solid behind. The process of settling the solid is called sedimentation, while the
process of pouring off the liquid is called decantation.
AIM:
To carry out the processes of sedimentation and of decantation.
MATERIALS:



4 x 100 mL beakers
1 x measuring cylinder
stirring rod



coarse gravelly soil e.g., aquarium gravel
fine clay soil
plastic teaspoon
PROCEDURE:
1.
2.
3.
4.
Copy the aim of this activity into your notebook.
Add about 70 mL of water to two of the beakers.
Add a spoonful of the coarse gravel to one beaker of water.
Add a spoonful of the fine clay soil to the other beaker of water. Mix both
well, using the stirring rod.
5. Add two teaspoonfuls of the fine clay soil to a measuring cylinder full of water
and shake well. (Leave this container to settle overnight)
 Which soil type settled most rapidly? Explain your answer.
 What special name is given to this process of settling?
6. Now pour the liquid from each beaker into the two empty beakers.
 What is the name of this process?
 Describe two examples where decantation is used in or around the
home.
 Draw simple diagrams to show the processes of sedimentation and
decantation.
13
Activity 7: Filtration
Sedimentation and decantation works well for separating large insoluble particles
from a liquid. However, very fine particles take a long while to settle. As well, the
act of decanting often stirs up the sediment again. Scientists need a better and
faster method. Filtration is one such method.
AIM:
To carry out the process of filtration.
MATERIALS:








4 x 100 mL beakers
filter paper
filter funnel
filter funnel stand
powdered chalk (coloured)
copper sulfate powder
popsticks
stirring rod
PROCEDURE:
1. Add about 50mL of water to two of the beakers.
2. Use a popstick to add some powdered chalk to one of the beakers.
3. Add some copper sulfate powder to the other beaker using a different popstick.
4. Set up the apparatus you need to filter each mixture.
5. Fold a filter paper in half then in quarters. Gently open out the filter paper to
form a hollow cone. Insert this into the filter funnel and dampen it lightly to hold
it in place.
6. Stir the chalk mixture thoroughly using the stirring rod before pouring it into the
filter paper. Be careful not to overfill the filter paper cone. Collect the filtrate in
one of the spare beakers.
7. Repeat this process for the copper sulfate solution collecting the filtrate in the
remaining beaker.
14
8. In your notebooks, under the heading ‘Filtration’ copy the aim for this activity.
9. Describe what happened to the insoluble chalk powder during the filtration
process.
10. Define what is meant by the term ‘residue’.
11. Describe what happened to the soluble copper sulfate during the filtration
process.
12. Explain the difference you noticed
when filtering these two mixtures, one a
suspension, the other a solution.
13. When should you use filtration as a
separation process? When is it not a
useful process?
14. Draw a fully labelled diagram to show
the apparatus used in filtration.
15
Activity 8: Centrifugation
AIM: To demonstrate how centrifugation can be used to separate substances.
MATERIALS:




filter paper
filter stand
filter funnel
centrifuge




flour
washed yellow sand
powdered blue chalk
clay

Try filtering a mixture of flour and water.
Report any difficulties you have with this procedure.

Your teacher will demonstrate how the process of centrifugation can be
used to quickly separate the flour from the water.

Try using this method to separate a mixture of sand, crushed chalk and
flour in water.

Does the speed with which the centrifuge is turned affect how well the
different parts separate? Try this out.

Ultra-high speed centrifuges spin at 80,000 revolutions per minute. Why would
this kind of centrifuge be better at separating particles than the
one you used?

Centrifugation is commonly used to separate suspended substances.
Can you think of some examples of situations where it is used?
16
Part B: Separating a Solute from a Solvent
Filtration did not work as a way of separating copper sulfate from water because the
particles of the solute were too finely divided when they were dissolved. They easily
passed through the filter paper.
How could you recover the solute from a
solvent?
If you have ever walked along rocky seashores
you would have noticed small puddles of
seawater drying out in the sun.
Does this give you a clue???
Snapping
Turtlebeaks!
This water
sure is salty!
17
Activity 9: Evaporation
AIM: To carry out the process of evaporation.
MATERIALS:





watch glass
Bunsen burner
tripod
gauze mat
bench mat




0.5M copper sulfate solution
evaporating basin
matches
safety glasses
PROCEDURE:
1. Pour a small amount of copper sulfate
solution into the watch glass and place it in
a safe place in the laboratory where it can
stand for several days to evaporate.
2. Half fill the evaporating basin with copper sulfate solution and then
place the basin on a gauze mat on the tripod ready for heating.
3. Light the Bunsen burner and gently heat the evaporating basin. When the
solution begins to boil withdraw the Bunsen from under the tripod.
Return the Bunsen burner as the boiling slows.
WARNING: DO NOT OVERHEAT
the basin may crack
tiny particles of the solute may spit out of the basin
wear safety glasses.
4. Continue this process of gentle heating until the solution is nearly
evaporated.
5. Withdraw the Bunsen altogether and let the heat from the basin
complete the evaporation process.
RESULTS
1. Under the heading ‘Separating a solute from a solvent: evaporation’
describe the process you observed.
2. During this process what happened to the a. solvent
b. solute
3. Draw a clearly labelled diagram to show a quick way to evaporate a solution.
18
Activity 10: Distillation
The evaporation process is useful for recovering the solute from a solution.
However, it is of no use if it is the solvent that needs to be recovered.
CHALLENGE
Can you suggest a way to get the solvent from a solution? Discuss your ideas with
the members of your group. Draw a simple diagram to show your method.
What goes up must come
down!
In the laboratory and in industry the method used is called distillation.
Basically distillation involves two steps:
1. evaporation of the solvent
2. condensation of the solvent.
19
The apparatus to do this is called a still. There are a number of types of stills. In the
production of whiskey, alcohol is distilled from fermented malt. The stills used are
very large and are made of copper or stainless steel.
In the science laboratory we use a type of still called a Liebig Condenser, named
after the person who invented it.
The Liebig Condenser
D
F
B
G
A
E
H
Look at this diagram very carefully. Think about the diagram
on the previous page and about your own diagram.
Brainstorm in your group to work out the role of each piece of apparatus shown
above. Report your ideas to the whole class. Your teacher will demonstrate how it
all works.
20
REVIEW:
1. Use the following key words to write a summary of the process of
distillation:
Condense
Solution
Evaporate
Condenser
Distillate
Cool
Heat
Cooling water
2. In this process what happens to:
a. the solvent?
b. the solute?
3. Why does the cooling water enter the condenser from the bottom and not from
the top?
4. What name is given to the water that has been purified in this process?
5. Write down at least two uses for this kind of water.
21
Library Research
Library Assignment - Separating in the Real World
Answer two of these questions. Each question should come from a
different section. Large, labelled and schematic diagrams will get
you lots more marks than none at all. Your assignment will
probably end up about two A4 sides long.
Decantation & Sedimentation
1.
2.
Septic tanks and sewerage treatment plants use sedimentation and decantation methods to
remove heavy solids. (yuk!!!) Draw a diagram and explain how it works.
Gold dust was separated from the dirt by 'panning', 'sluicing' and 'dry blowing' (not really
decanting) during the gold rush. Explain how these separation methods work.
Filtration
3.
4.
5.
Most cars have three ‘paper element’ filters. What are they and what do they do? Draw a
diagram showing how one of them works.
Bore water is sometimes called 'sand filtered'. What does this mean? Why, after all that
filtering is it sometimes undrinkable?
Use a diagram to explain how a swimming pool filter removes

Large leaves

Small leaves

Dirt
What is the purpose of the diatomaceous-earth in some swimming pool filters?
Evaporation and Distillation
6.
7.
8.
9.
Western Australia has several large salt farms where salt is separated from seawater.
Explain clearly how these operate.
In an oil refinery, crude oil is broken down into many parts like kerosene and oil by a
special distillation method. Draw a simple diagram of the apparatus used to do this and
briefly explain how it works.
Find out how "Stills" are used to produce spirits like whisky. Make sure you label all the
phases of the process on your diagram.
At the Bridestowe Estate at Nabowla in Tasmania, lavender oil is extracted from lavender
flowers by a special distillation process. Many other essential oils such as eucalypt and rose
hip oil are also collected this way. Explain how this is done.
Practical Work at Home
10.
Use water and several different types of common paper to try to separate green food
colouring by chromatography. Dry and stick your papers onto a page. Explain what you
have learned.
DIAGRAMS
DIAGRAMS DIAGRAMS
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DIAGRAMS DIAGRAMS
Activity 11: Chromatography
Two substances that are both dissolved in the one solvent can be separated by the
process of chromatography. This makes use of the differing ability of
particles to travel through another substance like paper or a tightly packed
powder.
Pencil
AIM:
To carry out the process of chromatography.
MATERIALS:
10 cm strip of strip of filter paper
250 mL beaker
black ball point pen
methylated spirit in a dropper bottle




Filter paper
strip attached
to pencil
Methylated spirit
PROCEDURE:
1. Use the pen supplied to rule a line across the strip of filter paper about
2 cm from one end.
2. Add about 1 cm of methylated spirit to the beaker.
3. Hook the other end of the filter paper strip over a pencil resting across the top of
the beaker so that the marked end of the paper just touches the methylated spirit
in the beaker. The line itself should not be immersed. Do not let the paper touch
the side of the beaker.
4. Over the next 5 minutes or so watch what happens to the ink line as the
methylated spirit moves up into the filter paper.
5. Under the heading ‘Chromatography’ draw a diagram showing what you did
and record you observations. You may wish to dry the paper and stick it into
your notebook.
INFERENCE:
Why did the ink behave this way?
Interested??


Try other ink colours to see how they separate.
Can you make a rainbow of colours on one strip of paper?
23
Investigation 1: Chromatography
Form a group of 3 students: one student should act as the leader, one as the
technician to collect and set up the equipment, the third should act as the reporter.
Question to investigate:
Do some papers work better than others when carrying
out the process of chromatography?
Your group's task:
1. Design a way of testing the question under investigation use these

headings:





Hypothesis
Aim
Materials
Method - make sure you identify the
 experimental variable
 dependent variable
 controlled variables
 control setup
Results - think about how you might best present these.
2. Each group member should carry out the investigation and write a
conclusion to the investigation.
Follow up activity:
Assess the written report of your neighbouring group - be tough but fair. Be
prepared to report back to the class on the strengths and weaknesses of their report.
24
Competition Time!!
Activity 12: Crystallisation
A solvent is something that dissolves
substances. Water is a good solvent because
many substances dissolve in water. It is often
called the ‘universal solvent’ for this reason.
When a substance dissolves in a solvent, a solution is formed. If you keep adding
more and more of a substance to a solvent, it will eventually become ‘full’ of the
substance. The scientific word for this is saturated. A saturated solution is one
where the solvent has dissolved as much of the
substance as it can at that temperature.
You can tell whether a solution is saturated by trying to dissolve more of
the substance in it.
When hot, a solvent will dissolve more of a solid than when it is cold.
The difference between dissolving sugar in hot and cold drinks is a good
example of this. More sugar can be dissolved in a hot drink.
If you dissolve as much sugar as possible in a hot drink then let it cool, the sugar
will crystallize from the solution. This is because the solution is already ‘full’ of
sugar at the higher temperature. As the solution cools the sugar that can no longer
be dissolved forms crystals.
AIM:
To use the process of crystallisation to separate a solute
the solvent it is dissolved in.
MATERIALS:









1 vial with cap
10 mL of water
1 plastic teaspoon
1 beaker, 250 mL, filled with water heated to about 70ºC (or a supply of
running hot water)
1 Petri dish
paper towel
potassium nitrate (KNO3)
1 measuring cylinder, 10 mL
1 hand lens.
25
from
METHOD:
1. Using the measuring cylinder, pour 10 millilitres of
water into the vial.
 Add one spoonful of the potassium nitrate.
 Put the cap on the vial and shake vigorously.
 If all the potassium nitrate dissolves, add
another spoonful and try to dissolve it by
shaking.
Continue this process until the potassium
nitrate will not all dissolve.
2. Hold the vial, with the cap on, under the hot water
in the beaker. Shake the vial as shown until any leftover potassium nitrate in the vial dissolves.
3. Pour half of the solution in the vial into the Petri
dish and put it in a safe place for later observation.
Replace the cap and hold the vial, containing the
other half of the solution, under cold running
water until crystals have grown.
OBSERVATIONS
1. Using the hand lens, examine some of the crystals
that form in the vial. Concentrate on their size and
shape. Try to sketch the different crystals.
2. After 24 hours examine the crystals that have formed
in the Petri dish. How do they compare with the ones
that formed in the vial?
Some solutions in nature cool more slowly than others. Usually the slower
the cooling, the larger the are the crystals which form.
3. How does this fit in with your observations?
How’s this………………
Imagine finding a crystal that was 4 metres in diameter. It would take you
four long strides to walk across it! Mica crystals nearly four metres across
have been found.
The largest single crystal ever found was about 13 metres long and had a
mass of 65 tonnes.
26
SUMMARY:
Under the heading ‘Separating by Crystallisation’ copy and complete the
statements that follow by filling in the missing words using the ones below:
fewer
slowly
1. Crystals form as a
saturated
solution becomes cooler.
2. This means that
solute particles can be held in solution.
They collect around a point to form a crystal.
3. Large crystals form when a solution cools
Review of Separation Methods
Match the phrase on the left with the most appropriate word on the right:
1.
Used to recover a solute from a solution.
a.
residue
2.
Used to recover the solvent from a solution.
b. centrifuge
3.
Remains in a filter paper after filtration.
c.
4.
Substance which passes through a filter paper.
d. distillation
5.
Pouring water off potatoes in a saucepan.
e.
Liebig condenser
6. Form when a solution evaporates.
f.
evaporation
7. Instrument that separates particles by spinning.
g. decantation
8. Instrument used in the laboratory for distilling.
h. filtrate
crystals
Check your work and then copy the statements into your workbook as a summary.
27
Summary of Separation Processes
Copy and complete this table:
Process
When used
Diagram of Process
1. Decantation
2. Filtration
3. Evaporation
4. Distillation
5. Centrifugation
6. Chromatography
28
Investigation 2: Investigating soft drink
Designing an investigation to separate the components of a soft drink
Background
Most of you drink soft drinks at least occasionally. They may taste pretty good – but
have you ever really stopped to think about what they have in them?
In this open investigation your task is to try to separate different components of a
soft drink and work out what ingredients it contains.
Your teacher will supply you with equipment you may use (although you don’t
need to use it all).
Equipment available
soft drink
filter stand
beakers
tongs
clay triangle
balloon
taper
small bottle
filter paper
Bunsen burner or hotplate
evaporating basin
salt
measuring cylinder
filter funnel
test tubes
test tube stopper with tubing
tripod
chromatography paper
capillary tubes or pipettes
Planning
It is important to think of a plan before you start. You might need to use a few
different methods to identify all components in your drink.
First brainstorm what might be in a soft drink.
What’s in a soft drink?
Obtain a copy of the worksheet: What’s in a soft drink?
29