KS3 Chemistry H2 – Energy from chemical reactions 8th January 2007

Combustion is the chemical reaction that takes place when a substance burns. The substance reacts with oxygen and energy is released as heat and light. Combustion is an important reaction as more than 90% of the world’s energy comes from burning fossil fuels like coal, natural gas and petrol. Where do fossil fuels come from and what other fuels are there? Using combustion

Fire triangle

Combustion Fuel + oxygen waste gases Energy is released

Equations for combustion Combustion, as the reaction of substance with oxygen, is also called oxidation. The products of oxidation are oxides. Coal is mostly carbon. The product of burning coal is a gas which turns limewater cloudy. What is the equation for burning coal? carbon dioxide oxygen carbon Many fuels are hydrocarbons, which means they are made up of carbon and hydrogen. When hydrocarbons burn carbon dioxide and water (hydrogen oxide) are produced. What is the equation for burning the hydrocarbon methane? carbon dioxide oxygenmethanewater

Build your Glossary Combustion Fuel Hydrocarbons Voltaic Cells Oxide Pollution Displacement reaction

Correct your Glossary... Combustion - The reaction of a substance with oxygen which releases heat and light energy. Fuel - A substance that is burnt to provide energy. hydrocarbons – Compounds that are made up of the elements carbon and hydrogen only. Voltaic Cell – Simple battery in which electricity passes between two metals placed in dilute acid.

Correct your Glossary... Oxide – A compound formed when a substance burns and joins with oxygen in the air. Pollution – The contamination of water, air or soil by harmful or toxic substances. Displacement reaction – A chemical reaction in which an element is removed from its compound by a more reactive element.