GRADE 7
Name:
Using insulating material
When you learnt about conduction, you learnt about good conductors and poor
conductors. You also learnt that poor conductors are also called insulators. Materials
that are poor conductors are used to prevent heat loss (such as in a flask) and to
prevent injury from burning (such as pot handles).
Insulating materials are good at keeping warm things warm and cold things cold. This
means they are good at preventing heat loss and heat gain.
Houses
Houses should be built from
materials that are poor
conductors of heat – so that
that they will be cool in summer
(when it’s hot outside) and
warmer in winter (when it is
cold outside). Most houses are
built from brick and cement,
which are poor conductors.
Ceilings of buildings
In many ceilings, there are layers of
insulating material placed on top of the
ceiling boards. This keeps the house
warm. All of the heat generated in
the house will rise to the ceiling by
convection. If there is no insulation,
the heat will travel through the
ceiling boards (by conduction) and
through the roof and out into the
atmosphere. When there is insulation,
the heat cannot pass through the ceiling
boards, so it is forced to stay in the house,
which will keep the house warm.
Cooler boxes and thermal flasks
Cooler boxes have a layer of insulating material that prevents heat from being
transferred into the box from outside. This material may be plastic or polystyrene.
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Grade 7 Term 3 Natural Science: Energy and Change: Heat Transfer: Insulation 2
Heat transfer: Insulation 2
GRADE 7
Grade 7 Term 3 Natural Science: Energy and Change: Heat Transfer: Insulation 2
Spongy or foamy materials, like polystyrene, are good insulators
because they have bubbles of air trapped in their structure.
This helps to prevent heat from passing through them.
Thermal flasks can be used for hot or cold
drinks. They also have a layer of insulating
material, but they use an even more powerful
method of insulation called a vacuum. There is
a space between the outer layer of material and the inner
layer. This space is sealed and is a vacuum.
(If you remember from our discussion about how heat is transferred by
the sun, you will remember that we said that it is difficult for heat to be
transferred across space because space is a vacuum – there is not air
through which heat can travel.)
Clothing
When you are cold, your body responds by making your
hair stand up. Your hair traps the warm air close to your
skin and warms you up. Clothes are made so that they
can do a similar thing by keeping the warmth our body
produces, instead of allowing it to be transferred to the
surroundings.
Some clothes, like coats, are made from a thick weave of
fabric that does not allow the warm air to travel through
it away from your body. Other clothes are made from a
lighter or thinner weave of fabric, such as fleece or wool. This fabric traps the warm
air our bodies produce and prevents it from escaping.
Activity 1: Answer these questions:
1) Read this scenario and answer the questions that follow.
Jack and his family live in an informal settlement. Their home is made of corrugated iron. In summer, their house is very hot, and in winter, it is very cold.
a) What is Jack’s house made of?
__________________________________________________________________
b) Is this material a good insulator or a good conductor of heat?
__________________________________________________________________
c) Why is Jack’s house very hot in summer and very cold in winter?
__________________________________________________________________
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_________________________________________________________________
_________________________________________________________________
2) Read this scenario and answer the questions:
Caleb is a firefighter. He and his team get called out to a
building that is on fire. He puts on his bunker gear,
including his pants and jacket made
from special material. He enters
the building with his gear on
and retrieves a person who is
trapped in the fire. He pulls
her out of the building; she is
conscious, but in shock. Caleb
takes off his jacket and wraps
it around her.
a) Why is it important for Caleb to wear his special clothing when entering a building on fire?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
b) Explain how the clothing protects him from the heat of the fire in the building.
__________________________________________________________________
__________________________________________________________________
c) Why does Caleb put the jacket around the person he rescued?
_______________________________________________________________
_______________________________________________________________
d) Explain how the jacket prevents the person from getting cold (as a result of shock).
_______________________________________________________________
_______________________________________________________________
© e-classroom 2014 www.e-classroom.co.za
GRADE 7
Grade 7 Term 3 Natural Science: Energy and Change: Heat Transfer: Insulation 2
What could Jack and his family do to prevent heat gain in summer and heat loss d)
in winter. (Tip: Use your knowledge about insulating materials.)
GRADE 7
Activity 1
1) Read this scenario and answer the questions that follow.
Jack and his family live in an informal settlement. Their home is made of corrugated
iron. In summer, their house is very hot, and in winter it is very cold.
a) What is Jack’s house made of?
Corrugated iron
b)Is this material a good insulator or a good conductor of heat?
It is a good conductor of heat.
c) Why is Jack’s house very hot in summer and very cold in winter?
Jack’s house has no insulation. The corrugated iron transfers heat out of his
home in winter, causing it to be very cold. It transfers heat into his home in
summer, making the house very hot.
d)What could Jack and his family do to prevent heat gain in summer and heat loss
in winter.
A layer of insulating material needs to be put inside Jack’s house, lining the
roof and walls. Materials may include newspaper, cardboard or polystyrene.
(This can be used as a research question or project for the learners to complete.
Have them investigate the advantages and disadvantages of using different
materials. Have them test which materials would be most effective, economical
and convenient. Have them build a model of the house with their preferred
insulation technique included.
There are many interesting and innovative ways this can be done – visit the link
below to see examples:
http://blog.greenhomebuilding.com/2007/12/using-earthbags-as-ceilinginsulation.html
2) Read this scenario and answer the questions:
Caleb is a firefighter. He and his team get called out to a building that is on fire. He
puts on his bunker gear, including his pants and jacket made of special thick material.
He enters the building with his gear on and retrieves a person who is trapped in the
fire. He pulls her out of the building; she is conscious but in a lot of shock. Caleb takes
off his jacket and wraps it around her.
© e-classroom 2014 www.e-classroom.co.za
Grade 7 Term 3 Natural Science: Energy and Change: Heat Transfer: Insulation 2
Answer Sheet
The special gear protects him from the heat, the flames and any debris
(fallen objects, broken windows, etc.)
b) Explain how the jacket protects him from the heat of the fire in the building.
The fabric of the jacket and pants is a good insulator. It does not allow the
heat to be transferred through to his body. This protects him from the heat
of the fire.
c) Why does Caleb put the jacket around the person he rescued?
He puts the jacket around the person to keep them warm.
d) Explain how the jacket prevents the person from getting cold (as a result of
shock).
As the jacket is a good insulator, it traps the person’s body heat which
does not allow body heat to be transferred through the jacket to the
surroundings.
© e-classroom 2014 www.e-classroom.co.za
GRADE 7
Grade 7 Term 3 Natural Science: Energy and Change: Heat Transfer: Insulation 2
a) Why is it important for Caleb to wear his special jacket and pants when entering
a building on fire?