Combustion Worksheet

Combustion (or burning, as it is more commonly known) is the reaction between a fuel and Oxygen which can create lots of energy.

The Oxygen required for this reaction comes from the air. The air is a mixture of gases. It is mainly composed of:

Nitrogen (about 78%), Oxygen (21%) and a small mixture of other gases such as Carbon Dioxide and Argon. This can be shown in a pie chart:

Pie chart of gases of the air

During combustion, oxides are also produced.

For example, when the flammable metal magnesium is burned, lots of light, heat and smoke are produced, but when the reaction is complete the white solid Magnesium Oxide will be clearly seen. This reaction can be seen in the 'sparklers' that are used on Bonfire Night.

Sparkler

This reaction can be shown in a word equation:

Magnesium + Oxygen Magnesium oxide

Please note that the light, heat and smoke are not included in the chemical (word) equation because they are not chemicals and all combustion reactions are irreversible.

The energy produced by combustion can be put to many uses - from heating your home and cooking your food, to powering your car. The fuels used to provide energy for these uses are not metals, like magnesium, but they are more likely to be petrol, diesel, natural gas etc...

Let's have a further look at COMBUSTION.

Which ONE of the following gases makes up most of the air?

Nitrogen

Oxygen

Carbon Dioxide

Air is a mixture of gases.

Shown on the right is the percentage of air that each gas makes up (by volume).

Match each of the gases on the left to the correct percentage on the right.

Column A	Column B
Oxygen	Less than 1%
Nitrogen	Less than 1%
Carbon Dioxide	78%
Argon	21%

Which of the following gases is required for a fuel to burn?

Nitrogen

Oxygen

Carbon Dioxide

Argon

Combustion is the reaction of a fuel with oxygen. This reaction produces lots of energy. Which TWO of the following are not powered by the energy produced by the combustion of a fuel?

car engine

gas boiler

solar-powered calculator

wrist watch

gas barbecue

Alcohol is a commonly-used fuel in Brazil to power cars. Alcohol burns with a blue flame to produce lots of heat, carbon dioxide (CO₂) and water.

Use this information to decide whether each of the substances listed below is a reactant or a product in the reaction.

Car manufacturers are developing cars that use HYDROGEN as a fuel. Hydrogen burns to produce only water and, therefore, doesn't contribute to pollution problems such as acid rain or climate change.

Use the table below to complete the equation for the combustion of hydrogen.

Hydrogen + A B

	Answer
A
B

ANSWERS

Question 1

Which ONE of the following gases makes up most of the air?

CORRECT ANSWER

Nitrogen

EDDIE SAYS

Air is mostly made up of the unreactive gas nitrogen. Packets of crisps contain 100% nitrogen gas as it doesn't react with the crisps, allowing them to stay fresher for longer.

ANSWERS

Question 2

Air is a mixture of gases.

Shown on the right is the percentage of air that each gas makes up (by volume).

Match each of the gases on the left to the correct percentage on the right.

CORRECT ANSWER

Column A	Column B
Oxygen	21%
Nitrogen	78%
Carbon Dioxide	Less than 1%
Argon	Less than 1%

EDDIE SAYS

The composition of air varies depending on temperature and altitude. The higher up you go the less oxygen the air contains. Weirdly there's loads more ARGON in the air (0.9%) than Carbon Dioxide (0.04%) - how many ordinary people have heard of argon and yet pretty much everyone has heard of CO₂!

ANSWERS

Question 3

Which of the following gases is required for a fuel to burn?

CORRECT ANSWER

Oxygen

EDDIE SAYS

Oxygen is required for a substance to burn. The higher the concentration of oxygen the better the fuel will burn.

ANSWERS

Question 4

Combustion is the reaction of a fuel with oxygen. This reaction produces lots of energy. Which TWO of the following are not powered by the energy produced by the combustion of a fuel?

CORRECT ANSWER

solar-powered calculator
wrist watch

EDDIE SAYS

Solar power harnesses energy from the sun and wrist watches use the energy produced by a chemical reaction within the battery (unless they're solar-powered too!).

ANSWERS

Question 5

Alcohol is a commonly-used fuel in Brazil to power cars. Alcohol burns with a blue flame to produce lots of heat, carbon dioxide (CO₂) and water.

Use this information to decide whether each of the substances listed below is a reactant or a product in the reaction.

EDDIE SAYS

The reactants are the chemicals that react to create one or more new products. So, here alcohol and oxygen are reacting together to release the energy stored in the fuel. Then the waste products CO₂ and water are left.

ANSWERS

Question 6

Tick the objects from the list below that could be used as a fuel.

CORRECT ANSWER

Petrol
Wood
Candlewax

EDDIE SAYS

A fuel is a substance that burns easily (reacts with oxygen) to release lots of energy. That means that it has to have the capacity to store lots of chemical energy. Weight for weight, petrol packs an incredible amount of energy into a small volume.

ANSWERS

Question 7

Car manufacturers are developing cars that use HYDROGEN as a fuel. Hydrogen burns to produce only water and, therefore, doesn't contribute to pollution problems such as acid rain or climate change.

Use the table below to complete the equation for the combustion of hydrogen.

Hydrogen + A B

CORRECT ANSWER

	Answer
A
B

EDDIE SAYS

Hydrogen is classed as pollution-free fuel, but the production of hydrogen involves the combustion of fossil fuels, which do contribute to pollution problems (such as acid rain and global warming).