# Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels

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Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels

Combustion, fuels and hydrocarbons
Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels When a substance burns, it is said to combust. Combustion is a rapid reaction between a substance and oxygen that releases heat and light energy. A fuel is a substance that reacts with oxygen (combusts) to release useful energy. Photo credit: Eric Terry Many fractions obtained from crude oil are used as fuels because they contain hydrocarbons that burn easily and release a large amount of useful energy.

Complete combustion of hydrocarbons
Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Plenty of air is needed to provide enough oxygen for a hydrocarbon fuel to burn completely. The blue flame of a gas hob or a Bunsen burner is an example of complete combustion of a hydrocarbon (in this case, natural gas). What are the products of the complete combustion of a hydrocarbon? Photo credit: Julian Spencer oxygen carbon dioxide hydrocarbon + water

Complete combustion of propane
Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Propane is a hydrocarbon used in camping gas. What is the equation for its combustion? oxygen carbon dioxide propane + water 5O2 3CO2 C3H8 + 4H20 How would the equations change if butane was used?

Products of combustion
Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Teacher notes This virtual experiment illustrates how the products of the combustion of a hydrocarbon can be determined. It should be made clear to students that air is sucked through the apparatus while the candle is burning.

Incomplete combustion of hydrocarbons
Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels If there is a shortage of air (oxygen), incomplete combustion of hydrocarbons takes place. Instead of producing just carbon dioxide and water, incomplete combustion also produces carbon monoxide and/or carbon (soot). It also releases less energy than complete combustion. Photo credit: Małgorzata Głuchowska ( Carbon monoxide is a poisonous gas because it reduces the ability of blood to carry oxygen.

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels
Teacher notes This true-or-false quiz could be used as a starter exercise to work on alternative fuels. Students could be given coloured traffic light cards (red = false, green = true) to vote on the statements shown. To stretch students, they could be asked to explain their voting.

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels
How soon will we be using alternative fuels?

The need for alternative fuels
Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Most vehicles in the world use petrol or diesel as a fuel. These are produced from crude oil, a fossil fuel. Although fossil fuels are convenient sources of energy, they are very polluting, and will one day run out. As a result, some people have already begun using alternative fuels to power their vehicles, such as biofuels and hydrogen. Photo credit: Witold Barski Why is it important to develop and use these fuels before oil supplies run out?

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels
What are biofuels? Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Biofuels are renewable fuels produced from plant material, such as agricultural crops. Two types of biofuel used in vehicles are bioethanol and biodiesel. They can be safely combined with normal petrol or diesel and used in conventional engines to reduce levels of harmful emissions without causing engine damage. Photo credit: Ana Schaeffer

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels
What is bioethanol? Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Bioethanol is an alcohol produced by the natural fermentation of the carbohydrates (such as starch) in sugar beet/cane or wheat crops. Photo credit: Ivana De Battisti ‘Flexi-Fuel’ vehicles, fitted with modified fuel injection systems, can run on E85 fuel (85% bioethanol, 15% petrol), which cuts carbon dioxide emissions by 70% compared to normal petrol-engine cars.

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels
What is biodiesel? Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Biodiesel is produced by chemically reacting vegetable oils or animal fats with alcohol and a catalyst. The process can be completed in 12 hours. Biodiesel can be mixed with conventional diesel, which significantly reduces emissions, especially toxic hydrocarbons, particulates and carbon monoxide. Photo credit: Andre Veron There are few garages in the UK that sell biodiesel. Home-made fuels, usually from waste vegetable oils, are heavily taxed.

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels What are some of the advantages of using biofuels? Biofuels are carbon neutral: the carbon released during combustion comes from the carbon dioxide the plants took in when they were growing. Storage, transport and distribution costs are low as biofuels can be handled in the same way as conventional fuels. Photo credit: Charles Bensinger/Renewable Energy Partners of New Mexico/NREL Triple biofuels dispenser at Baca Street Biofuels Stations. By-products of production, such as pressed seedcake, can be burnt in power stations instead of fossil fuels or used a animal feed.

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels What are some of the disadvantages of using biofuels? Although biofuels themselves produce relatively little when combusted, their production needs energy from fossil fuels. There are few UK producers of biofuels, and only small quantities of fuel are made. Biofuels therefore need to be imported, mainly from Brazil and South-East Asia. The high demand for land to plant biofuel crops can lead to deforestation and habitat loss, for example in Malaysia.

What are hydrogen fuel cells?
Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Hydrogen fuel cells are electrochemical devices like batteries, which produce electricity by converting hydrogen and oxygen into water. A big advantage of hydrogen fuel cells is that they do not create any pollution: the only emission they produce is water vapour. Photo credit: Warren Gretz/NREL A 5kW fuel cell manufactured by Plug Power. The chemicals inside fuel cells are constantly replenished, so unlike batteries, fuel cells never run flat or need recharging.

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels What are some of the disadvantages of fuel cells? The production, storage and distribution of hydrogen for use in fuel cells relies heavily on energy from fossil fuels. Pure hydrogen is expensive and highly flammable. One way around these problems is to replace hydrogen with a more convenient substance. Methanol, natural gas and propane have all shown potential for use in fuel cells. Photo credit: SunLine Transit Agency/NREL The ThunderPower fuel cell bus was developed under a joint venture by Thor Industries and ISE Research, participating in a six month demonstration at SunLine Transit Agency.

Opinions on alternative fuels
Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Teacher notes This voting activity enables the individual opinions of the class to be represented graphically. It could be used as a precursor to a debate on the use of alternative fuels, such as how important the financial cost is the most important factor.

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels
Glossary (1/2) Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels biodiesel – A biofuel made by chemically reacting plant oils or animal fats with alcohol and a catalyst. bioethanol – A biofuel made from the natural fermentation of the carbohydrates in plants such as sugar cane/beet and wheat. biofuel – A renewable fuel made from biological material, such as plant matter. combustion – A rapid reaction between a substance and oxygen that produces heat and light energy. complete – The type of combustion that only produces carbon dioxide and water.

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels
Glossary (2/2) Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels fuel – A substance that provides useful energy when it burns. fuel cell – A device that produces electricity from a chemical reaction, e.g. between hydrogen and oxygen. hydrocarbon – A molecule containing only hydrogen and carbon. incomplete – The type of combustion that produces carbon monoxide and/or soot in addition to carbon dioxide and water.

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels
Anagrams Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels

Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels
Multiple-choice quiz Boardworks GCSE Science: Chemistry Combustion and Alternative Fuels Teacher notes This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of combustion and alternative fuels. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.