A reaction in which a fuel burns in oxygen and releases energy.

Why is combustion called exothermic?

It transfers energy to the surroundings, so the temperature rises.

What are the possible products of incomplete combustion?

Carbon monoxide, carbon (soot) and water.

Write the symbol equation for the complete combustion of methane.

CH₄ + 2O₂ → CO₂ + 2H₂O

What colour is the flame in complete and in incomplete combustion?

Blue in complete combustion, yellow in incomplete combustion.

When does incomplete combustion happen?

When the oxygen supply is limited.

Fine particles of carbon made in incomplete combustion.

How can you put out a fire using the fire triangle?

Remove one side: the fuel, the oxygen or the heat.

Why is carbon monoxide dangerous?

It is toxic: it stops the blood carrying oxygen around the body.

Why is carbon monoxide hard to detect?

It is colourless and has no smell.

How can the risk of carbon monoxide poisoning be reduced?

Good ventilation, servicing appliances and fitting a carbon monoxide alarm.

CombustionIB MYP Sciences: Flashcards

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What is combustion?

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What is combustion?: A reaction in which a fuel burns in oxygen and releases energy.
Why is combustion called exothermic?: It transfers energy to the surroundings, so the temperature rises.
What are the products of complete combustion of a hydrocarbon?: Carbon dioxide and water.
What are the possible products of incomplete combustion?: Carbon monoxide, carbon (soot) and water.
Write the symbol equation for the complete combustion of methane.: CH₄ + 2O₂ → CO₂ + 2H₂O
What colour is the flame in complete and in incomplete combustion?: Blue in complete combustion, yellow in incomplete combustion.
When does incomplete combustion happen?: When the oxygen supply is limited.
What is soot?: Fine particles of carbon made in incomplete combustion.
What are the three sides of the fire triangle?: Fuel, oxygen and heat.
How can you put out a fire using the fire triangle?: Remove one side: the fuel, the oxygen or the heat.
Why is carbon monoxide dangerous?: It is toxic: it stops the blood carrying oxygen around the body.
Why is carbon monoxide hard to detect?: It is colourless and has no smell.
How can the risk of carbon monoxide poisoning be reduced?: Good ventilation, servicing appliances and fitting a carbon monoxide alarm.

Exam questions on Combustion

A chef in Lagos cooks on a gas hob that burns natural gas, which is mainly methane. When the air holes at the base of the burner are open, the flame is blue and the pan stays clean. When the air holes are closed, the flame becomes yellow and the base of the pan is coated in a black deposit.
Explain why the flame is yellow and produces a black deposit when the air holes are closed.2 marks
A family in Montreal runs a gas heater in a small bedroom during a cold winter. The windows are sealed to keep the heat in. During the night, a carbon monoxide alarm in the room sounds loudly.
Suggest two ways in which the family could reduce the risk of carbon monoxide poisoning.2 marks
Alana, a student in Wellington, investigates how long a candle burns under glass jars of different volumes. She lights three identical candles, covers each with an upturned jar and times how long it takes for each flame to go out. The 250 cm³ jar gave 8 seconds, the 500 cm³ jar gave 17 seconds and the 1000 cm³ jar gave 33 seconds. She tested each jar once.
Describe the trend in Alana's results and explain it using the fire triangle.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).