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Burning Fossil Fuels (Key Stage 4)
Teacher guidance and student stimulus sheets
These activities look at what happens when fossil fuels burn. There are two parts to
the activity:
• demonstration of burning fuels
• paper-based student activity to look at the breaking and formation of bonds
during combustion.
This activity relates to the former function of the Avenue as a coke-producing site.
Curriculum
The activities can be used to address areas of the 14-16 science and chemistry
specifications that look at fossil fuels, reactions, equations and energy changes and
energy level diagrams.
The topic lends itself to a further debate on the use of energy for heating in houses
and other buildings. How is the use of fossil fuels affecting the atmosphere? How can
the burning of fossil fuels be reduced by, for example, the use of insulation or
alternative energy sources.
Risk assessment
Before carrying out any activity, teachers must produce a suitable risk assessment.
This should be compatible with any local rules or restrictions. Sufficient precautions
must be in place when demonstrating the burning of fossil fuels and dealing with
flammable materials. Some points to consider include:
Fuels may be burned on a metal lid and disposed of in a metal bucket full of water
after use to ensure they have extinguished.
Take care with cobalt chloride paper. Keep handling to a minimum and wash hands
after use.
Students and the demonstrator must wear eye protection.
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Demonstration of burning fossil fuels
Note that a risk assessment and suitable precautions must be taken when handling
flammable materials and apparatus that may become hot when performing this
demonstration. Ensure the room is well ventilated.
to vacuum
pump
Resources
Set up the apparatus as shown
in the diagram below on a heat-resistant mat.
heat-resistant
glass funnel
limewater
anhydrous cobalt
chloride paper
burning fuel
Students observe any deposits on the funnel, changes in the cobalt chloride paper
(water) and in the limewater (carbon dioxide). Use fresh limewater and dry cobalt
chloride paper with each different fuel. Do not burn materials that will give off toxic
fumes, such as plastics. Suggested fuels include:
• Coal (1cm3 is sufficient)
• Wood (wooden spill)
• Candle (wax)
• Methane (Bunsen burner) – try with blue flame and also with white, sooty
flame to demonstrate incomplete combustion in reduced oxygen.
Discuss the observations to come to the conclusions that products of burning
hydrocarbons are water and carbon dioxide. Incomplete combustion also results in
particulates (sooty carbon).
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Combustion reactions
These paper-based activities allow students to investigate the reactions taking place
when hydrocarbons burn in oxygen.
In its simplest form, students rearrange the molecules according to the word
equation.
This can be extended by having students physically break and make bonds using
scissors and glue or sticky tape. This approach can also be used to illustrate the
conservation of atoms and balanced equations.
The activity can lead into a discussion of energy changes and energy diagrams.
Resources
• Student worksheet
• Molecules sheet (additional sheets if balancing equations)
• Energy change stimulus sheet
• Scissors
• Sellotape
Combustion reactions
When fuels burn, they combine with oxygen from the air.
These reactions gives out heat. They are called exothermic reactions.
Task
Use the printed molecules to show what is
happening during the combustion reactions
listed below.
For each reaction, use the printed molecules to show the reactants and the
products that are formed.
Answer these questions for each reaction.
1. What are the reactants and products?
2. How could you test the products to identify them?
• Hydrogen gas burning in oxygen
3. Write a word equation for the reaction.
4. Write a formula equation for each reaction.
• Methane gas burning in oxygen
• Propane gas burning in oxygen
• Coal burning in a rich supply of oxygen
Think about the reaction of coal burning in air.
5. Suggest what would happen if coal was burned with a limited supply
of oxygen.
What problems could this cause?
6. What other problems are caused by the burning of fossil fuels?
coal
oxygen
water
methane
hydrogen
carbon dioxide
propane
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Exothermic reaction energy changes
An exothermic reaction can be represented with an energy level diagram. This is one for burning methane in oxygen.
The energy of the products is lower than the energy of the reactants. The energy cannot simply disappear. It is given out as heat.
Activation energy starts the reaction.
energy
It is the energy taken in which is needed to break the bonds
between the oxygen, carbon and hydrogen atoms.
Change in energy
At the end of the reaction, this is the difference in
energy between the reactants and the products.
Use this information to calculate the
amount of energy released when
hydrogen is burned in oxygen.
Energy
taken in
(kJ/mol)
Energy
given out
(kJ/mol)
1,370
1,856
This is sometimes called 'delta H' - ΔH
Energy of reactants
Energy of products
Energy is given out as the bonds
form to make the products.
reaction progress
Draw and label an energy level diagram
showing the energy changes during an
endothermic reaction. This is one that
takes in more energy than it gives out.