User:Berbatov/Temp/Topic.doc
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LESSON ON CONDUCTION FOR LOWER SECONDARY STUDENTS
Topic: Transfer of thermal energy (Conduction)
Class: Lower Secondary students (Form II)
Time: 50 minutes
Aim: To introduce the concept of transfer of thermal energy (conduction)
Prior Knowledge:
Students should be familiar with the concepts of temperature and energy (heat energy).
They should also know how to read a thermometer.
Learning Outcomes:
After this lesson, the students must be able to:
1. define conduction
2. appreciate that conduction occurs mostly in solids
3. give examples of conductors
4. differentiate between good conductors and bad conductors
5. give uses of good conductors and bad conductors
Teaching Strategies used: Questioning, Brainstorming, Guided discovery, Group work,
expository, demonstration.
Teaching Aids: Beakers, Water, Bunsen burners, Tripods, Wire Gauze, Thermometer, Metal
Rods made of different materials, Wax, Thumb tacks, Stand, Clamp, Blackboard, Chalks.
References: MIE Textbook- Science Form II, New Secondary Science Book I, Pan Pacific
Publications
Methodology: Starts on next page
Time and Teaching Strategies used
5 mins.
First teacher asks the students for
their attention and get ready for the
class,
Description of activities/Procedure
Students will note the objectives in their copybooks.
Teacher tells the students about the
objectives of the lesson.
1. Ask students to fill their beakers with water.
2. Heat their beakers with a Bunsen flame.
3. What do you notice?
Expected ans: The water becomes hot.
10 mins group work/questioning
4. How can you verify it?
The students will be provided with
beakers and thermometers. Testing Expected ans: By touching the beaker. By using a
of prior knowledge, questioning.
thermometer.
Teacher will move around to ensure
that everything is ok. (safety
measures)
Here teacher explains the use of a mercury thermometer
which can be used to measure temperature.
5. Ask the students to verify this by putting the
thermometer vertically with the help of retort stands in
contact with the water.
6. What happens to the mercury level?
Ans: It rises
7. Why is this so?
Ans: Because it is in contact with the water and has
absorbed the heat from the hot water. Ask the students to
note the temperature of the water.
Teacher will clearly explain that there is transfer of
thermal energy from the Bunsen flame to the water and
then when the thermometer is placed in the water, there is
transfer of heat from the water to the thermometer. This is
why the mercury level will rise. Hence the temperature
increases.
The purpose of doing this activity is to test prior
knowledge that is whether they know about measurement
of temperature which they have already learnt in Form I
and also to make them more familiar with the use of a
thermometer and a Bunsen burner. Also it is a good way
to introduce the concept of conduction since the same
apparatus will be used in the next activity.
Time and Teaching Strategies used
20 mins
Guided discovery, questioning,
expository
Description of activities/Procedure
The beakers will be used (A temperature of 90°C will be
used in this activity.)Each group will be provided with a
metal rod and a glass rod.
1. Ask the students to hold the rods. Teacher will ask if
they are hot or cold.
Introduction of the concept
conduction
Ans: Cold
10 mins
2. Now ask them to put the rods into the beaker without
letting water splash out and ask them to wait for 1 min.
Demonstration showing conduction
in a metal rod. (To check
understanding)
3. Tell the students to see that one end of the rod is in
water and the other end is outside. Will the ends of the
rods which are inside the beaker become hot?
Ans: Yes
15 mins
4. Will the ends which are outside the water become hot?
Guided discovery, questioning
Ans: Yes
Introducing the concept good
conductors.
5. Tell the students to verify their statements by touching
the ends which is outside the beaker.
5 mins
6. According to you why is this so?
Brainstorming, Group work
Expected Ans: Some will say that the water
Uses of good conductors and bad
conductors of heat
has made the metal rod hot. The high fliers will say that
since the metal rod is in contact with the water, there is
transfer of thermal energy.
10 mins
7. Which end is hotter, the glass one or the one which is
made of metal?
Recapitulation
Ans. The metal rod is hotter.
8. Why do you think this is so?
Ans. No ans.
9. What is it inside the metal that makes it become hotter
than the glass rod?
Ans: No answer
At this point, the teacher introduces the concept of free
electrons and tells the students that in a metal there are
free electrons and that when a metal is heated at one end,
the free electrons acquire thermal energy and hence they
move towards the other end of the metal.
Teacher asks the students to take all these observations
under those which they have already taken during the
beginning of the lesson.
8. Ask the students if the metal rods have moved from
their original positions.
Ans: No
Then the teacher introduces the concept of conduction.
Teacher writes the definition of conduction. It is the
transfer of heat from a hot region to a cold region without
movement of the material itself. Tell the students that
conduction occurs mostly in solids.
After each activity, the materials are put away from the
students, otherwise they will have the tendency to play
with all the materials and also for safety reasons.
Teacher will take one metal rod and will clamp it. Wax is
applied on to the free end.
At different positions, thumb tacks are placed. The set-up
is as shown:
[[Image:]]
By adjusting the stand, the end of the metal rod which
does not contain wax is heated with a Bunsen burner.
Ask the students to observe what happens and write it in
their notebooks.
Ans: The wax melts and the thumb tacks fall. Here the
students’ observation is very important because they will
notice that the thumb tacks will fall in a certain order.
From the diagram, it will be from the left to the right.
A demonstration will be shown to the students. The
experiment will consist of heating 6 rods made of 6
different materials. The materials are iron, aluminium,
copper, wood, glass, plastic. The rods will be coated with
wax and a thumb tack fitted to each off them. (a lab
attendant will help)
1. Are all solids good conductors of heat?
Ans: Yes. Wrong answer
2. The rods are heated with the help of Bunsen burners. It
is made sure that the rods are heated at the same
temperature.
The students are told to observe what happens and to note
their observations.
3. What do you observe?
Ans: The thumb tacks fall off the rods.
4. Have you observed the order in which the thumb tacks
fall?
Ans: Yes
Here most of the students will have noticed that the
thumb tacks fall off the aluminium, copper and iron rods
first and then a longer time is taken for the thumb tacks to
fall off the glass, wood and plastic rods.
The rods are then placed in the order in which the thumb
tacks have fallen.
Then the students will record the order in their
copybooks.
At this point, the teacher will introduce the concept of
good conductors and bad conductors.
The rods from which the thumb tacks have fallen first are
good conductors of heat.
5. With what materials have the rods been made?
Ans: iron, aluminium, copper
6. What are they?
Ans: Most will say metals.
At this point teacher tells the students that metals are
good conductors of heat.
7. What about the rest?
Ans: They are bad conductors
Teacher will tell the students that a special name is given
to bad conductors and the name is thermal insulators.
Teacher will ask students to draw two columns and the
headings will be good conductors and bad conductors
(insulators).
Then the students will write down examples of good and
bad conductors. One student will come on the blackboard
to write the names and then after verification, the students
will correct their list in their respective copybooks.
Students are now familiar with good conductors and bad
conductors. Now they will work in groups to discuss
some uses of good conductors and bad conductors which
they will write in their copybooks. One example of a use
of a good conductor will be frying pans which are copperbased. Similarly one example of a use of a bad conductor
will be that of wood which is used to make handles of
domestic equipment ( e.g casserole)
A summary of the different concepts is done together
with some short notes.
Follow up:
1. Worksheets containing small exercises on conduction will be given to students.
The small exercises will consist of multiple choice questions, short structured questions and also
fill in the blank type questions.
2. The use of audio-visual equipments where the students will be able to see some
demonstrations of conduction.
3. Use of the internet and animations to show to students some simulations on temperature
change, transfer of energy.
4. Ask students if they have encountered real life situations about conduction. A good example
will be the cooking of food at home. Students will be asked to describe what are the processes
involved and the related concepts.
5. Students will also be asked to do a small project on what they have learnt about conduction
and also to do some additional research.
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This page was last modified on 22 December 2010, at 11:59.
This page has been accessed 197 times.
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