Gill
Science
Stage 4
S
Mixture separation
Part 2 – What are mixtures?
Number: 43922
Title: Mixture Separation
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Extract from Science Syllabus Years 7-10 © Board of Studies, NSW 2003
Overview
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Contents – Part 2
Lesson 6: Particles in pure substances and mixtures
3
Classifying substances
5
Diagrams of pure substances
6
Diagrams of mixtures
7
Lesson 7: Properties of pure substances
11
Physical properties
11
Chemical properties
12
Physical and chemical properties
13
Lesson 8: Identifying pure substances
Checking properties
Lesson 9: Investigating mixtures around us
How can you identify mixtures?
15
15
21
21
Lesson 10: Estimating mineral in a rock mixture
25
Suggested answers – Part 2
29
Exercises – Part 2
33
Part 2: What are mixtures?
1
2
Mixture separation
Lesson 6: Particles in pure
substances and mixtures
Where can we find substances?
Everything around us is made of substances/matter/material/chemicals.
Look at some examples of sentences using these words.
Activity: Describing substances
Suppose you have a necklace made of gold. You could write these sentences
about the necklace.
The necklace is an example of matter.
•
The gold in the necklace is an example of matter.
•
The material used to make the necklace is gold.
•
The necklace is made of a substance called gold.
•
The necklace is made of a chemical called gold.
Here is one sentence about a copper bracelet.
•
The bracelet is an example of matter.
Finish these sentences about the copper bracelet.
•
The copper in the bracelet is an example of _________________ .
•
The ___________________ used to make the bracelet is copper.
•
The bracelet is made of a ____________________ called copper.
•
The bracelet is made of a ____________________ called copper.
Here is one set of possible answers. Since the words mean the same, you
could change the sentences around.
•
The copper in the bracelet is an example of matter.
•
The material used to make the bracelet is copper.
•
The bracelet is made of a substance called copper.
•
The bracelet is made of a chemical called copper.
The necklace and the bracelet were each made from one substance. The
necklace was made from gold and the bracelet was made from copper.
Part 2: What are mixtures?
3
You can write the same sort of sentences about things made from more than
one substance.
For example, you could write these sentences about milk.
•
Milk is an example of matter.
•
Milk is made of materials.
•
Milk is made of substances.
•
Milk is made of chemicals.
Cordial is also made of more than one substance.
Activity: Using the terms substances/matter/material/chemicals
Write four sentences about cordial.
This sentence should contain the word matter.
_____________________________________________________________
This sentence should contain the word substances.
_____________________________________________________________
This sentence should contain the word materials.
_____________________________________________________________
This sentence should contain the word chemicals.
_____________________________________________________________
Are these the sentences you wrote?
Cordial is an example of matter.
Cordial is made of substances.
Cordial is made of materials.
Cordial is made of chemicals.
Remember that the words matter, material, substance and chemical are
often used to mean the same thing. Don’t be confused when you meet these
words later.
4
Mixture separation
Classifying substances
There are many ways to classify substances. One way of classifying
substances is into two groups based on their purity.
One group contains all the pure substances. Gold and copper are examples
of pure substances. Pure substances contain one type of material or chemical
only.
The other group contains substances that are impure (not pure). Impure
substances are called mixtures. Mixtures are made when two or more pure
substances are present together. Milk and cordial are examples of substances
that are mixtures.
So, a substance can either be a pure substance or a mixture. Pure substance
refers to substances that are made from only one type of chemical. A
mixture is a mix of more than one chemical. As a result a mixture is not
pure; a mixture is an impure substance.
Activity: Classifying substances
Use the information you have just read to fill in the boxes in this key.
Check your answer.
Part 2: What are mixtures?
5
Diagrams of pure substances
Let’s find out what pure substances are like if you could look at them really,
really closely and see the particles.
A pure substance has one type of particle only. A particle can consist of:
•
single atoms like
•
atoms joined together like
or
or
or
.
Note that atoms joined together in particles can be identical or different.
C
A
B
The pure substances A and
B are made up of one atom
only.
D
The pure substances C and
D consists of particles
made up of two atoms
joined together.
E
The pure substance E
consists of particles
made up of three
atoms joined together.
All these examples of matter or materials would be pure substances. Let’s
look at why.
This diagram represents a pure substance because
it contains particles that are all the same.
All the particles are single atoms like this
.
This diagram represents a pure substance because
it contains particles that are all the same.
All the particles are single atoms like this
.
This diagram represents a pure substance because
it contains particles that are all the same.
All the particles are made up of two atoms joined
together like this
.
6
Mixture separation
This diagram represents a pure substance because
it contains particles that are all the same.
All the particles are made of two atoms joined
together like this
.
This diagram represents a pure substance because
it contains particles that are all the same.
All the particles are made of three atoms joined
together like this
Diagrams of mixtures
A substance is a mixture if it contains two or more pure substances. So the
particles in a mixture would not all be alike. We would see two or more
different types of particles in mixtures.
This diagram represents a mixture because it
contains two types of particles. One particle looks
like this and the other particle looks like this
. The particles are not joined together, so they
represent two different pure substances.
Remember in a pure substance all the particles are identical. In a mixture
there are two or more different sorts of particles. A particle can be made up
of a single atom, two or more identical atoms joined together or two or more
atoms of different types joined together.
Activity: Mixture diagrams
Fill in the spaces in the sentences.
The diagram represents a _______________ because it
contains _______________ types of particles. This means it
contains two _______________substances.
One particle looks like this _______________ and the other
particle looks like this _______________.
Did you have this answer?
The diagram represents a mixture because it contains two types of particles.
This means it contains two pure substances. One particle looks like this
and the other particle looks like this
Part 2: What are mixtures?
7
Does this diagram represent a pure substance or a mixture?
__________________________________________________
Give a reason for your answer.
_____________________________________________________________
_____________________________________________________________
The diagram represents a mixture because it contains two different types of
particles. One particle looks like this and the other particle looks like this
.
Can you distinguish a pure substance from a mixture? This means, are you
clear about the difference between them? Try this test to make sure.
Activity: Test on particles in pure substances and mixtures.
1
Complete the definitions for a pure substance and a mixture by using the
sentence parts below.
two or more
types of substances
contains
of substance only
one type
A pure substance _______________________________________________
____________________________________________________________ .
A mixture _____________________________________________________
____________________________________________________________ .
2
Now you will draw two diagrams. One diagram will represent a pure
substance and the other will represent a mixture of two different pure
substances. Invent your own symbols for the particles in the substances.
A pure substance
Why is this a diagram of a pure substance?
_________________________________________________________
8
Mixture separation
A mixture of two pure substances
Why is this a diagram of a mixture?
_________________________________________________________
Check your answers.
Complete Exercise 2.1: Particles in pure substances and mixtures.
Part 2: What are mixtures?
9
10
Mixture separation
Lesson 7: Properties of pure
substances
Suppose you have just made a new friend. If you want to tell someone about
your new friend, you could describe the person's physical features
(appearance) or behaviour with people.
When you describe pure substances, you can also describe their physical
features or the way they behave with other chemicals. The physical features
of pure substances are called their physical properties. The way they
behave with other substances is called their chemical properties.
A pure substance always has one fixed set of properties because it contains
one substance only.
However, the properties of a mixture vary. The properties depend on the
particles in the mixture and the proportions of each. A mixture of 50% sugar
and 50% water has different properties from a mixture of 1% sugar and 99%
water.
Physical properties
Some physical properties such as state or odour can be observed just with
your senses. Others, such as the boiling point (temperature when a liquid
changes to a gas), need an instrument such as a thermometer.
Smell and taste can be dangerous properties to observe. Even very small
amounts of some substances can make you ill.
You should never taste an unknown substance. It can also be very dangerous
to take a deep sniff of an unknown smell, particularly if you suffer from
asthma. You can safely smell most substances by waving your hand gently
over the container, smelling the air you wave towards your nose. You might
like to practise this using vinegar or perfume.
Sometimes you will be asked to taste a substance in this unit, but the general
rule is never taste an unknown substance.
Part 2: What are mixtures?
11
Activity: Detecting or measuring physical properties
Write each property in the correct space in the table under the list.
colour
size
hard
no smell
sweet
boiling point
bitter
smooth
smelly
soft
shiny
rough
melting point
sour
salty
lets light through
Method of detecting or measuring
the property
Physical properties detected or
measured
sight
touch
hearing
smell
taste
instruments
Check your answers.
Chemical properties
A chemical property is a description of a substance’s behaviour with other
chemicals such as oxygen or water or air.
The changes or reactions that a substance undergoes are called its chemical
properties. Note that if you try to change a substance and nothing happens
you get no reaction. This is also a chemical property of a substance.
Suppose you heat liquid water. The water changes into steam, which is
water in the form of a gas. When the steam touches a cool surface it changes
back into liquid water. You have not made a new substance when you heat
water. The chemical property you have observed is that water is not
changed when you heat it.
Now, suppose you heat sugar. At first it will melt to form liquid sugar. So
far you have not formed any new substance. But if you keep heating the
sugar it starts to turn black and smell awful. Now you have made a new
black substance that is different from sugar. The chemical property you have
observed is that sugar changes when you heat it.
The experiments in the table below are investigating one chemical property.
The chemical property is whether the substance reacts with vinegar.
12
Mixture separation
Chemical properties of copper and magnesium
Substance
What you do
What you observe
Chemical property
copper
put vinegar on it
there is no change
copper does not react
with vinegar
magnesium
put vinegar on it
fizzing and the magnesium
eventually disappears
magnesium reacts with
vinegar
Activity: Chemical properties
Chemical properties of paper and concrete
Substance
What you do
What you observe
Chemical property
paper
set fire to it
the paper burns
the paper can be burned
concrete
set fire to it
the concrete does not burn
concrete cannot be
burned
These experiments are investigating one chemical property. The chemical
property is whether ____________________________________________ .
Chemical properties of starch and glass
Substance
What you do
What you observe
Chemical property
starch
put iodine on it
a black colour forms
starch reacts with iodine
glass
put iodine on it
there is no change
These experiments are investigating one chemical property. The chemical
property is whether ____________________________________________ .
Check your answers.
Physical and chemical properties
Can you distinguish between the physical and chemical properties of a
substance? (Distinguish means say how things are different.)
Activity: Physical and chemical properties
Complete these sentences by crossing out the wrong term.
When we observe physical properties, we do/do not change the substance
permanently. When we observe chemical properties, we try to change the
substance into a new substance. An example of a physical property of a
substance is its colour/whether it can be burnt and an example of a chemical
property of a substance is its colour/whether it is changed by acids.
Part 2: What are mixtures?
13
We do not change the substance permanently. When we observe chemical
properties, we try to change the substance into a new substance. An example
of a physical property of a substance is its colour and an example of a
chemical property of a substance is whether it is changed by acids.
Activity: Test on physical and chemical properties
1
2
Use the words and phrases in the list below to complete the following
sentences.
whether it burns
hardness (whether it scratches)
chemical
state (whether it is solid, liquid or gas
physical
whether it reacts with acids
a
Observing the _______________ properties of a substance does not
change the substance.
b
Observing the _______________ properties of a substance may
change the substance.
c
These are two examples of physical properties of substances:
_____________ and _______________.
d
These are two examples of chemical properties of substances:
______________________ and _______________________.
Tick the properties in the list that are physical properties of substances.
melting point
how hard it is
colour
sweet smell
how well it burns
its reactions
sour taste
Check your answers.
Now you can use what you know about physical and chemical properties to
complete the next activity.
Complete Exercise 2.2: Physical and chemical properties.
14
Mixture separation
Lesson 8: Identifying pure substances
Pure substances contain one substance only. Mixtures are formed when
there is more than one pure substance in the material. However, you cannot
always see the different substances that make up a material, so your
definition is not much help in deciding if a material is a pure substance or a
mixture. You have to work like a detective and use clues to help you decide.
Checking properties
Pure substances contain one substance only. So, pure substances have one
set of properties. This means that they have one melting point, one colour,
one hardness, one taste and so on for all the properties of the material.
Activity: Distinguishing between pure substances and mixtures using
properties
Answer each question explaining your reason(s).
1
Is the material in this photograph a pure substance or a mixture?
_________________________________________________________
2
Tess wanted to know if a white material was a pure substance or a
mixture. She heated it and found that part of it melted at 45°C and the
rest of the material melted at 85°C. Is the material a pure substance or a
mixture?
_________________________________________________________
Part 2: What are mixtures?
15
3
Hans believed that his material was a pure substance because it was all
one colour. When he carried out more tests, he found that part of the
material was soft and part of the material was very hard. Is the material
a pure substance or a mixture?
_________________________________________________________
Check your answers.
What are crystals?
An easy way to distinguish between some pure substances and mixtures is
looking for the presence of crystals.
Many solids are made of small pieces. When the little pieces have a regular
shape, the pieces are called crystals. Only pure substances have crystals. A
crystal contains one pure substance only.
Activity: Looking at crystals
What you will need:
•
a hand lens or a magnifying glass
•
table salt
•
some flour from your kitchen (any kind will do)
•
two pieces of paper or cardboard, preferably dark coloured.
What you should do
1
Put the salt and flour onto separate pieces of paper. If you can find
some dark coloured paper or cardboard, you will find the activity easier.
2
Do you know how to use a hand lens properly? A hand lens or
magnifying glass should be held close to your eye, not the thing you are
looking at. Then you should move your head up and down until the
thing you are looking at is ’clear’ or in focus. You can practise using a
hand lens correctly by looking at your skin.
3
Now use the hand lens to have a look at the flour. Remember what the
flour looks like and then look at the salt.
Here are two diagrams of what you might see through the hand lens or
magnifying glass.
16
Mixture separation
1
Which diagram looks most like the salt?
_________________________________________________________
Did you think that the salt looks more like the diagram on the left?
2
Now tick the statements below that describe the salt. You may tick
more than one statement.
Most of the salt crystals look like small cubes.
Most of the salt crystals have flat, smooth surfaces.
Most of the salt crystals have no regular shape.
The salt crystals have dull surfaces.
The salt crystals have shiny surfaces.
The first, second and last statements are correct.
3
Substances that are made of crystals are said to be crystalline. Is salt a
crystalline substance?
_________________________________________________________
Salt is a crystalline substance because it is made of crystals.
All crystals have a regular shape, but they do not have to be shaped like
cubes.
Why are crystals important?
Not all substances are made of crystals. But if a material is crystalline (made
of crystals), it can help you to decide if it is a pure substance or a mixture.
All the crystals in a pure substance are the same shape and colour. So if a
material is made of one type of crystal only, it must be a pure substance.
Some mixtures are crystalline, but they contain crystals that have different
shapes and colours. So, if a material is made from different types of crystals,
it must be a mixture.
Part 2: What are mixtures?
17
Activity: Using crystals to distinguish pure substances and mixtures
Use your understanding of crystals to answer the questions below.
1
Do you think that table salt is a pure substance?
_________________________________________________________
2
Do you think the rock in this photograph is a pure substance or a
mixture? _______________________________________________
Crystalline rock
Check your answer.
Activity: Test on crystals in pure substances and mixtures
1
This is what Alide saw when she used a hand lens to look at the
contents of a jar.
a
Does the jar contain a pure substance or a mixture? Give a reason
for your answer.
______________________________________________________
______________________________________________________
18
Mixture separation
b
Is the white powder a pure substance or a mixture? Give a reason
for your answer.
______________________________________________________
______________________________________________________
c
Is the clear material a pure substance or a mixture? Give a reason
for your answer.
______________________________________________________
______________________________________________________
d
Which material would you describe as crystalline?
______________________________________________________
______________________________________________________
2
Geoff also looked at some material he found in a jar. This is what he
saw.
He could not say whether the material was a pure substance or a
mixture of two or more white substances. What does he have to do to
find out?
_________________________________________________________
_________________________________________________________
_________________________________________________________
Check your answers.
Complete Exercise 2.3: Investigating soil.
Part 2: What are mixtures?
19
20
Mixture separation
Lesson 9: Investigating mixtures
around us
Very few things around you or that you use, eat or drink are pure
substances. They are mostly mixtures.
How can you identify mixtures?
Sufun was interested in finding out more about air. To her, all the air around
her looked the same. She could not see any different parts in the air.
Sufun decided to do an investigation to test a chemical property of air. The
experimental set up is shown in the diagram below.
Sufun's experimental set up at the start of the investigation
Part 2: What are mixtures?
21
What happened after a few minutes of Sufun’s investigation
Activity: What is in the air?
Use the diagrams to answer the following questions about Sufun’s
investigation.
1
Describe any changes that you can observe.
_________________________________________________________
The candle went out and the water went up into the upside down
measuring cylinder.
Sufun thought that part of the air was used up to burn the candle.
2
What does this tell you about the air?
_________________________________________________________
Air contains more than one part, so air is a mixture.
Sufun used a chemical property to find out if air had more than one part. She
found that part of the air is used in burning but most of the air is not.
Do you think tap water is a pure substance or a mixture? You will know if
you are correct after you have done this activity.
Activity: What is in our drinking water?
What you will need:
22
•
a soft cloth such as a tea towel
•
two clean, dry glass jars.
Mixture separation
What you should do:
1
Clean the glass jars. Wipe them so that there are no smears or marks left
on the glass.
2
Choose a warm place to perform this activity. Then put one or two
drops of tap water into one glass jar. Place the jar on its side on top of
the soft cloth. The water should form a tiny pool on the side of the glass
jar. The cloth prevents the jar from rolling.
Do you think this investigation is a fair test? Can you think of what you
should do to make the investigation a fair test? Write down your
suggestion.
_________________________________________________________
_________________________________________________________
You should leave a clean, dry glass jar in the same place, in case
something in the air affects the results of the investigation.
3
Get the other clean, dry glass jar. Do not put any water into it. Lie it
beside the first glass jar. Leave both jars in the warm place for a few
hours or until your next science lesson. You’ll know that the activity is
finished when the first jar has dried.
4
Compare the two glass jars.
_________________________________________________________
You should see some brown or white substances inside the glass jar
which had the water. The other glass jar should be clean.
5
What can you say about tap water? Do you think it is a pure substance
or a mixture?
_________________________________________________________
Tap water is a mixture. It is made of more than one substance – the water
that evaporated and the substances that were left on the side of the jar.
You may have known that town water has substances added to it. Perhaps
you have read about things that are added to drinking water? Water
authorities and councils add chlorine to kill ’germs’ in the water and often
fluorine to make our teeth strong.
Complete Exercise 2.4: Mixtures.
Part 2: What are mixtures?
23
24
Mixture separation
Lesson 10: Estimating mineral in a
rock mixture
The Earth is made up of many things, e.g. air, water and soil. Air, drinking
water and soil are all mixtures. What about the solid parts of the Earth, the
rocks? Are they pure substances or mixtures of substances?
Look at the photographs of three rocks following to decide if there is more
than one substance present and if the rock is a pure substance or a mixture.
Activity: The parts of rocks
Conglomerate
1
How many different substances can you find? __________________
2
Do you think the rock is a pure substance or a mixture?
_________________________________________________________
Granite
Part 2: What are mixtures?
25
3
How many different substances can you find in granite?
_________________________________________________________
4
Do you think granite is a pure substance or a mixture?
_________________________________________________________
Gneiss
5
How many different substances can you find in gneiss?
_________________________________________________________
6
Do you think gneiss is a pure substance or a mixture?
_________________________________________________________
It is easy to see that conglomerate is a mixture because it is made up of
small pieces of other rocks. Granite and gneiss are also mixtures because
they contain crystals with different colours and shapes. The crystals in rocks
are called minerals. Minerals can be thought of as building blocks for rocks.
Minerals
26
Mixture separation
7
Study the photograph of the minerals. Can you give a reason for saying
that minerals are pure substances?
_________________________________________________________
Each mineral is a crystal that has one shape.
Many minerals are valuable because people use them in some way. Minerals
are examples of resources because they are useful, valuable substances.
Some minerals are very beautiful and we use them as jewellery. Diamonds
and rubies are examples of minerals we use in this way. Others can be
processed to give us useful materials such as metals.
Does the amount of mineral in a rock matter? It does if you are trying to
take out some valuable materials from the rocks. Rocks that contain usable
amounts of valuable minerals are called ores.
This activity shows one way of estimating the amount of a mineral in a rock.
An estimate is somewhere between a guess and an accurate measurement.
Activity: Estimating amounts of minerals
On the squared paper below is an outline of a rock. Marked on the rock is
the valuable mineral A. If there is more than 25% of mineral A, then a profit
can be made from mining the rock. Is it worthwhile mining the rock to
extract mineral A?
1
First, estimate the area covered by the rock. Do this by counting all the
squares that are completely covered by the rock. ________________
2
Now count all the squares that are more than half covered by the rock.
Squares that are more than half covered _________________________
It is likely that the number of squares more than half covered are
balanced by the number of squares less than half covered. Since you are
making an estimate, you can ignore the squares that are less than half
covered.
Part 2: What are mixtures?
27
3
Write down the total number of squares you have counted. __________
4
The rock is equal to the total number of squares.
Total area covered by the rock. Remember to include the unit (cm2).
_________________________________________________________
Now you have to work out how much of mineral A there is in the rock.
5
Count all the squares that are covered or more than half covered by the
dark mineral A. This will be the area of the mineral A on the surface of
the rock that can be seen.
Area covered by the mineral A ________________________________
6
Now calculate the percentage (%) of the rock that is mineral A.
% of rock that is mineral A =
area covered by mineral
× 100
total area of rock
=
Will you make money by mining the rock? __________________________
Check your answers.
Complete Exercise 2.5 How much mineral?
28
Mixture separation
Suggested answers – Part 2
Activity: Classifying substances
Activity: Test on particles in pure substances and mixtures
1
A pure substance contains one type of substance only.
A mixture contains two or more types of substances.
2
Your diagram of a pure substance can contain single atoms or atoms
joined together. Here are three different, correct answers. Atoms joined
together can be identical or different.
Your diagram of a mixture can contain single atoms or atoms joined
together but there must be more than one type of particle. Here are two
examples of correct answers.
Part 2: What are mixtures?
29
Activity: Detecting or measuring physical properties
Method of detecting or
measuring the property
Physical properties
sight
colour, size, lets light through, shiny
touch
hard, smooth, soft, rough
hearing
–
smell
no smell, smelly
taste
sweet, bitter, sour, salty
instruments
boiling point, melting point
Activity: Chemical properties
Chemical properties of paper and concrete
Substance
What we do
What we observe
Chemical property
paper
set fire to it
the paper burns
the paper can be burned
concrete
set fire to it
the concrete does not
burn
concrete cannot be burned
These experiments are investigating one chemical property. The chemical
property is whether the substance can be burned.
Chemical properties of starch and glass
Substance
What we do
What we observe
Chemical property
starch
put iodine on it
a black colour forms
starch reacts with iodine
glass
put iodine on it
there is no change
glass does not react with
starch
These experiments are investigating one chemical property. The chemical
property is whether the substance reacts with iodine.
Activity: Test on physical and chemical properties
1
a
Observing the physical properties of a substance does not change
the substance.
b
Observing the chemical properties of a substance may change the
substance.
These are two examples of physical properties of substances:
hardness and state.
These are two examples of chemical properties of substances:
whether it burns and whether it reacts with acids.
c
d
30
Mixture separation
2
Tick the properties in the list that are physical properties of substances.
melting point
colour
how well it burns
sour taste
how hard it is
sweet smell
its reactions
Activity: Distinguishing between pure substances and mixtures
using properties
1
The material is a mixture because different parts have different
appearances.
2
The substance is a mixture because different parts melt at different
temperatures.
3
The substance is a mixture because different parts have different
hardness.
Activity: Using crystals to distinguish between pure substances
and mixtures
1
Table salt is a pure substance because there is only one type of crystal.
2
The rock is a mixture because it contains crystals of different shapes
and colours. The different crystals are different pure substances.
Activity: Test on crystals in pure substances and mixtures
1
a
The jar contains a mixture because it contains substances with
different appearances.
b
2
The white powder could be either a pure substance or a mixture.
You cannot tell from the appearance of the powder.
c The clear material is a pure substance because it is made of
crystals.
d The clear substance is crystalline because it is made of crystals.
Geoff has to observe or measure other properties of the substance. For
example, he could find out if different parts of the substance have one
or more melting points or if they behave the same way chemically.
Part 2: What are mixtures?
31
Activity: Estimating amounts of minerals
Squares covered by the rock = 20
Squares more than half covered by the rock = 13
Total area covered by the rock = 33 cm 2
Area covered by the mineral A = 3 cm 2
3 ×100
% of the rock that is mineral A =
33
= 9%
This is less than the 25% needed to make mining the rock profitable.
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Mixture separation
Exercises – Part 2
Exercises 2.1 to 2.5
Name ________________________________________________________
Teacher ______________________________________________________
Exercise 2.1: Particles in pure substances and mixtures
These shapes represent the particles in six different pure substances.
Which of the diagrams below represent pure substances and which represent
mixtures? Give a reason for each answer.
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
Part 2: What are mixtures?
33
Exercise 2.2: Physical and chemical properties
A student wrote this description of a substance. Read the description,
noticing which properties are physical properties and which are chemical
properties. Then answer the questions under the description.
I observed the substance and wrote down its colour. Then I tried to look
through the substance to see if light could pass through it. I found that I
could not burn the substance and when I dropped acid on it, it fizzed. I
also measured the melting point of the substance.
1
Name two physical properties mentioned by the student.
_________________________________________________________
_________________________________________________________
2
Name two chemical properties mentioned.
_________________________________________________________
_________________________________________________________
3
Name another physical property that the student could have described.
_________________________________________________________
_________________________________________________________
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Mixture separation
Exercise 2.3
Investigating soil
Cuz was interested in gardens and soil. He wanted to know if soil is a
mixture. You should be able to answer his question after this activity.
What you will need:
•
a hand lens or a magnifying glass
•
a teaspoon
•
about a teaspoonful of soil
•
a sheet of white paper.
What you should do:
1
Get about a teaspoon of soil from the garden or from a pot plant. Put the
soil on the piece of white paper.
2
Spread the soil out a bit and then use your hand lens to look at the soil.
3
Sketch what you can see. How many different substances can you
identify?
4
What do you want to tell Cuz about soil? Include your reason(s).
_________________________________________________________
_________________________________________________________
_________________________________________________________
Part 2: What are mixtures?
35
Exercise 2.4
1
2
Mixtures
Can you remember the meanings of some scientific terms? Draw a line
to match each term below with its meaning.
crystal
a basic building block of rocks
mineral
a regular shaped piece of a pure substance
mixture
an impure substance
property
containing one kind of particle only
pure
a feature that can be observed with the senses
Name three examples of common mixtures in nature.
_________________________________________________________
_________________________________________________________
3
Mixtures are often made in a kitchen.
a
b
Give an example. _______________________________________
Why do you think that it is a mixture? _______________________
______________________________________________________
______________________________________________________
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Mixture separation
Exercise 2.5 How much mineral
1
Calculate the percentage of valuable mineral B in this rock.
mineral B
Total area covered by the rock =
Area covered by the mineral B =
Percentage of mineral B in the rock =
2
=
Technology makes tasks easier or more convenient. Technology
provides opportunities for you to use your imagination and produce
creative solutions.
Draw a labelled diagram of equipment that could be used to measure
the amount of dark mineral B in a light coloured rock.
The equipment in your diagram does not have to be equipment that you
have used. It could be equipment that you have read about or seen. Just
imagine that you are an inventor trying to overcome a problem. How
could technology be used to measure the amount of dark mineral B in a
light coloured rock?
Part 2: What are mixtures?
37
38
Mixture separation