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Unit
11
Mixtures
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Unit
11
Mixtures
Focus
The purpose of having this unit is to provide opportunities for students to
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Identify some common mixtures from daily lives.
Describe aqueous mixtures in terms of solute, solvent and solution.
Identify situations where the process of filtration, sedimentation, sieving, chromatography,
evaporation, crystallization and magnetic attraction are appropriate to separate components
of mixtures.
Teaching Considerations
First Period
It’s a mixed up world
To begin the topic, it would
be useful to carry out a
brainstorming session with
students. So that you get a
clear idea of how much they
are aware of the concept.
Mixture is quite a common
word in daily life. These
types of words are often
misunderstood by many
students even after studying. So it is very useful to
find out their level of
understanding and make
them clear about what it
means scientifically.
After the brainstorming
session, explain the key
points given in the sub-unit in the textbook pages 120-121 and let them do the question given.
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Second Period Mixtures (practical activity)
Preparation for the lesson:
Crucible, bar magnet, three Petri dishes, spatula, iron filings sulphur powder.
The main purpose of this activity is for students to find out one property of mixtures on their own
(i.e. Separate components of mixtures keep their special properties). So your
job is to guide them and see whether they can come up with the property of the mixture.
Third Period
Seperating mixtures
Preparation for the
lesson:
Collect as many things as
possible for students to
carry out a separating
activity. For example, different size and type of coins,
rice and sand, different size
and type of balls etc.
This is again a very simple
and easy topic. There is no
need to go into explanation.
It would be better to give
students hands-on activity
and let them have and carry
out the activity. (You can get
more ideas from the textbook pages, 122-123)
Arrange the things you collected at different corners of the class room and let each group sort them
out or separate them out using the things provided.
When every one completes all the activities, then you can have a discussion on separating
mixtures. It is important to stress some of the key words like: decanting, filtration, suspension,
residue and filtrate. Students need to be clear about these words.
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Forth Period
Separating sugar from rice (practical)
Preparation for the lesson:
The things needed are listed in the activity book page 86.
This activity can be done by students in groups and let them answer the questions that follows on
page 87 in the Activity book.
The main idea they should get from this activity is how to separate a solid from a solution.
Fifth Period
Solids in liquids
The main idea students
learn in this topic is that
some are soluble while
others are insoluble in
water. And there are ways
that you can make things
dissolve faster.
Some of the key terms that
students should know are:
soluble, insoluble,
saturated, dissolve, solvent,
solute and solution.
Students might have some
idea about dissolving. So it
would be better if you start
the lesson by a
brainstorming activity.
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Sixth Period
Investigate dissolving (practical)
Preparation for the lesson:
Salt, sugar, and one type of chemical (powder) e.g. Copper sulphate.
This activity should be done by students. They should plan the activity themselves and teacher
should guide them and see that their plan is well and appropriate. This activity may take two periods, so it would be better if you carry out this activity in a double period. Otherwise, you could plan
the activity in one period and carry out the activity in the next period the following day.
Seventh Period Investigate dissolving (practical) Activity 2
Preparation for the lesson:
Sand, salt, iodine, ethanol, oil copper sulphate.
This activity can be carried out by the teacher as a demonstration, if you don’t have enough
material for all the students to do group work. But you should let students observe and write their
observation on their own.
Eighth Period Investigate dissolving (practical) Activity 2
The important point in this
lesson is to make connection with the concept of
evaporation of water and
how it can be used in daily
life. So first it is important
that they become familiar
with the term. Then they can
understand the separation
techniques more easily.
At the beginning of the
lesson, find out how much
they know about this
concept. Some students
might come up with
interesting ideas. If so you
could use their examples of
evaporation. It would
motivate students to
participate in such
discussion.
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Ninth Period
To get the water back
It might be a little bit difficult for students to understand this concept compared to evaporation. So
you have to be more careful and spend more time explaining condensation. .
There is a diagram under the heading “What happens if you get lost”, on page 129 in the textbook.
Let students explain this diagram in their own words.
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Tenth Period
What’s in the mixture...
This is another very useful
technique of separation.
Children need to be aware
of this method too. Using
the ideas given in the textbook, you can demonstrate
the formation of coloured
rings and let them write
their explanation in their
own words for the question
given under the heading,
“be a detective”.
Eleventh Period What’s in the mixture? (practical)
You can explain crystallization in this period and let students carry out separation activity using the
chromatography method given in the Activity Book page 90.
Twelfth Period
What’s in the mixture? (practical)
If you have enough material for students to do in groups, it would be better for students to do
themselves, if not this activity can be done as a demonstration. But they need to answer the
questions at the end of the activity by themselves.
Find The Mystery Word, Page 94 in the Activity book this activity can be done as homework.
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Assessment and Evaluation
In the assessment techniques that you use, you should see that students
• Identify some common mixtures.
• Describe aqueous mixtures in terms of solute, solvent and solution.
• Identify situations where the process of filtration, sedimentation, sieving, chromatography,
evaporation, crystallization and magnetic attraction are appropriate to separate components
of mixtures.
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