Name:
We use fuels everyday as sources of useful energy.
The definition of fuel is as follows:
l It is material used for burning as a fire or as a source of power or heat for example
wood, coal, paraffin or gas
l Food as a source of energy is a fuel
l Material used as a source of nuclear energy is a fuel
Fuels as sources of useful energy
Wood: we burn wood when making a fire. Fire provides us with heat and light, as
well as a method of cooking food.
Fire provides light
and warmth
Fire provides a method of
cooking food
Wood comes from trees. Plants and trees use light energy from the sun, as well as
carbon dioxide and water to grow. This energy is then stored in their leaves, roots
and other parts of the plant. Wood also contains this energy and when we burn the
wood, the stored energy changes into light and heat.
Complete the sentence: Energy from the
which is released as
when we burn
the wood.
is stored in the trees
and
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Grade 5 Term 3 Natural Sciences and Technology: Stored energy in fuels
GRADE 5
Stored Energy In Fuels
Wax
Wax from a candle is burnt
to provide light. There is
stored energy in the wax.
When the wax is burnt,
the stored energy changes
into light (output energy).
Paraffin
Coal
Paraffin is a fuel that
contains stored energy.
Paraffin is burnt in
paraffin lamps and stoves
to provide us with energy
in the form of light and
heat (output energy).
Coal is a type of fossil
fuel that is also burnt to
provide us with heat.
The heat from coal can
be used to cook our
food and warm our
houses (output energy).
Coal is burnt at an
electrical power station
in large quantities to
make electricity.
Gas Food Gas is burnt to provide
People need food to live,
light, warmth and to
because food provides us
cook food. There is stored with stored energy that
energy in the gas. When it our bodies can change
is burnt the stored energy into useful energy which
changes into light and
we need when we run,
heat (output energy).
jump, breathe, learn and
everything else that we do
(output energy).
Petrol
Petrol or diesel is used in
cars and trucks to make
them operational. The
stored energy in the
fuel is changed into
movement energy of
the car or truck (output
energy).
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GRADE 5
Grade 5 Term 3 Natural Sciences and Technology: Stored energy in fuels
Stored Energy In Fuels (2)
How fossil fuels are formed
1. Fossil fuels were made from prehistoric plants and animals, which got their energy
from the sun.
2. The plants and animals that died, sank to the bottom of the water and over
millions of years, the plant/animal layers were covered by sand and water and buried.
3. The debris was buried deeper and deeper under the ground where the
temperature is much hotter than on the surface. These materials underwent chemical and physical changes and changed into fossil fuels.
4. Other fossil fuels are natural gas and crude oil.
Fossil fuels get their name “fossil” because they
are made from plants and animals that were
alive a long time ago.
Fun Activity: Measuring the output energy we get from burning different fuels
What you will need:
1. A cork, a needle
2. Peanuts, a piece of wood and a candle
3. A large metal can like a coffee tin
4. A small metal can (250g: make sure the label is removed)
5. A can opener, a hammer and a large nail
6. A metal spike/nail longer than the diameter of large can
7.150ml of water, a thermometer and a lighter
What to do
1. Push the eye of the needle into one end of the cork. Then push the sharp end of the needle into the peanut. Because the peanut is so frail it may break. Keep
trying with other peanuts until you get it right.
2. Use the can opener to remove both ends of the large can.
3. Use the hammer and nail to punch holes in the bottom of the large can. These are air holes.
4. Take the small can and punch two holes near the top of the can exactly opposite each other.
5. Slide the metal spike through the two holes in the small can and then pour
150ml of cold water into it.
6. Measure the temperature of the water with the thermometer and record it on the table below.
7. Light the peanut (heat is the input energy). The peanut can be difficult to light so keep trying. It will eventually start burning.
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GRADE 5
Grade 5 Term 3 Natural Sciences and Technology: Stored energy in fuels
Stored Energy In Fuels (3)
8. When the peanut starts burning, carefully place
the large can over the peanut. Balance the small can inside the big can as shown in the
diagram. The small can must be a short
distance above the peanut.
9. Let the peanut heat the water until the peanut stops burning. Stir the water and then measure the temperature of the water and record it in the results table.
10. Repeat the experiment with the wood and the candle and record your findings in the table below.
11. Remember to use quantities of the other
fuels which are similar in size to the peanut,
and to always start with a cold can of water.
Results Table
Peanut
Wood
Candle
Input energy
Output energy:
1. Temp of water before heating (°C)
2. Temp of water after heating (°C)
3. Change in water temp (°C)
Questions
1. Which fuel contained the most amount of energy?
2. How did you determine this?
3. Where did the energy in the wood originally come from?
4. When you lit the fuel, what happened to the stored energy in it?
The lighting of the wood, candle and peanut required a small amount of energy, but
the fuel released more energy than what was put in. The difference between the
energy you put in and the energy the fuel released is the amount of energy stored in
the fuel.
In conclusion: The OUTPUT ENERGY from a fuel is GREATER THAN the
INPUT ENERGY needed to make the fuel burn.
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Grade 5 Term 3 Natural Sciences and Technology: Stored energy in fuels
GRADE 5
Stored Energy In Fuels (4)