Insulators and Conductors
Objective: Describe insulators and conductors. Identify materials
that are good insulators and conductors.
Heat Transfer
• Heat always moves from a warmer place to a
cooler place.
• Hot objects in a cooler room will cool to room
temperature after the hot object transfers some of
their heat to the cold object.
• Cold objects in a warmer room will heat up to
room temperature.
Why does metal feel colder than wood, if they
are both at the same temperature?
Metal is a conductor, wood is an insulator. Metal
conducts the heat away from your hands. Wood
does not conduct the heat away from your hands as
well as the metal, so the wood feels warmer than
the metal.
At home energy is TRANSFERRED in
lots of ways. Look at this saucepan
where potatoes are being boiled.
Heat energy is being transferred from the
electric ring to the glass hob.
Heat energy is being transferred from the
glass hob to the metal saucepan.
Heat energy is being transferred from the
metal saucepan to the water and potatoes.
Then can I transfer the
potatoes from the pan
to my stomach?
What do we call things that allow heat energy to transfer easily?
They are called
conductors.
Solid fuel stove
Good conductors
feel cold when there is
no source of heat. They
don’t retain heat but let
it be transferred away.
Metal hob
The heat energy is transferred
from the burning fuel, to the metal
hob, to the metal saucepan and
kettle and then to the water. Heat
energy is being transferred from
the water to the spoon in the
Sometimes we don’t
want heat to be
transferred, we want
to keep the heat in.
What do you know
about all these
things?
Hats, coats, gloves and scarves are all insulators. They make it difficult
for heat energy to be transferred from your body to the cold air, so they
keep you warm.
What is a conductor?
• A conductor is something which allows electricity
to flow through.
• An example of a conductor is:
–
–
–
–
–
–
Scissors
Paper clip
Aluminum foil
Iron
Steel
Copper
Look at these containers. They will be filled with hot water.
Which ones do you think are conductors that will allow the transfer of
heat energy most easily?
How will I know
which containers conduct
heat energy most easily?
glass
Paper cup
Clue
Polystyrene
cup
Metal
mug
Pottery
mug
Plastic
mug
Examples of Conductors
• Metal
• Glass
•Paper
Electrical Conductor Example:
Objects that allow
electrical charge to
flow easily
Example:
The coil from a
electric heater gets
hot and conducts
electricity well
Conductor: a material that transmits electrical energy
easily
Metals make the best conductors
Property of Electrical Conductor:
In all good conductors
electric current flows
through them without
resistance
Example: Electricity flows
through the coil in the
power line coils easily
and without resistance
Good Conductors
• Metal is a good conductor of
electricity
What is a Insulator?
• An insulator is what help keeps electricity from
not flowing
• Examples of insulators are:
– Cotton
– Plastic
– Rubber
Insulators
• We use INsulators when we want to keep
the heat IN – so the amount of
heat/temperature stays about the same
OR we use an insulator when we DO NOT
want the heat to pass through easily, so
we won’t be burnt.
– Example: Thermos, Oven Mitts, Styrofoam
cup with hot coffee, Winter Jacket, Rubber,
blanket.
Look at these things.
These are insulators too.
What do they do?
Tea cosy, burger box and thermos flask all prevent the transfer of heat.
Thermos
• A thermos is a
container that is
capable of keeping hot
items hot and cold
items cold.
• A thermos, a cooler or
even an insulated cup
works by preventing
transfers of heat!
What are Insulators?
• Insulators are materials that do not allow heat
to move easily through them.
Conductors & Insulators
Insulator: a material that resists or blocks the flow of
electrons through it
Good Insulators:
Why Metals Feel Cool to the
Touch at Room Temperature
• Room temperature is cooler than human body
temperature.
• Heat is ONLY noticed when there is a transfer!
• Metals quickly conduct heat from your body
throughout the metal (since it is taking heat, it
feels cold).
• Wood and plastic don’t conduct heat quickly, so
not as much is taken from your skin.
• Good insulators normally have a lot of space for
air, because gases doesn’t conduct heat as well as
solids.
These are pictures of conductors
and Insulators
Conductors
Insulators
Insulator or Conductor??
Here is a fun activity. Use your fingers to find out which materials
are good conductors and which are good insulators. Use a table
like this one.
Conductors
Feel cold to touch.
Metal scissors
Insulators
Do not feel cold to touch.
Cotton T shirt
Things I am not sure about
1. Cotton ball
2. Metal scissors
3. Metal cookie sheet
4. Notebook paper
5. Rubber duck
6. Curling Iron
7. Glass Cup
8. Electric Heater (coils)
9. Plastic Trash Can
10. Metal Wire
11. Plastic Spatula
12. Copper Penny
13. Iron frying pan
14. Drawing chalk
15. Eye on the stove
Procedure
Draw the following picture in your science
journal.
Let me demonstrate…
Set up the equipment as shown and tape the
wires to the battery.
•Does anything happen?
•Does the banana allow electricity to flow through the
circuit and light the bulb?
•Is it a conductor or an insulator? Why or why not?
Inquiring Minds Want to Know!
Conductor or Insulator? That is the question!
Now take the bag of
materials and spread
them out in front of you.
Draw the following table
in your journal.
As you test each item,
record whether it was a
conductor or and
insulator with a
Item
Spoon
Paper clip
pencil
Rubber
band
eraser
Foil
Nail
coin
Conductor
Insulator
Did the
bulb
light?
Now its your turn…
Use of a circuit tester: To test whether the
material is a good electrical conductor.
Example of a circuit tester
Reducing Heat Loss From The Home
• Heat can be lost through many places at
home. These include:
–
–
–
–
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Roof
Walls
Gaps around doors and windows
Floors
Windows
Reducing Heat Loss From The Home
• We can reduce heat loss from our homes by using
different methods of insulation.
• These include:
– Double glazing
– Loft Insulation
– Cavity Wall Insulation
– Carpets, Curtains, Draught Excluders
Expansion and
Contraction
Expansion and Contraction
• Expand- increase in
volume (get larger),
• Contract- decrease
in volume (get
smaller)
• Materials expand or
contract when
subjected to changes
in temperature.
• Most materials
expand when they are
heated (particles move
farther apart), and
contract when they are
cooled (particles move
closer together).
Bridges are made from materials
that contract and expand as the
temperature changes, so they
cannot be fastened firmly to the
bank of a river or lake.
The photographs below show an
expansion joint at the end of a bridge
in winter and in summer.
(a) Which season is shown in each
picture? Explain how you know.
(b) Why do you suppose concrete
roadways and sidewalks are laid in
sections with grooves between them?
#1
#2
Expansion and Contraction
in Gases
#1
#2
If you put gases in a flexible
container such as a balloon,
you can see that they
expand and contract much
more than solids when the
temperature changes.
Expansion and
Contraction of Liquid
As the thermometer liquid
moves up the glass tubing
(the bore), it takes up more
space. In other words, the
liquid expands as it warms.
As the thermometer cools,
the liquid contracts, so it
moves back down the tubing.
The liquid must be
contracting as it cools.
Exception
Water doesn’t expanded or
contract.