Reactivity 1.3 - Energy from fuels

• A fuel is a source of chemical energy that releases energy when oxidised
• Fuels can be renewable (eg. biofuels) or non-renewable (eg. fossil fuels)
• Combustion reactions involve reactive metals, non-metals, and organic compounds heated in oxygen with the evolution of heat
• In combustion reactions, oxygen is the oxidising agent and its oxidation state changes from 0 to -2
• Choice of fuel is determined by factors like availability, ease of extraction, storage, environmental and social effects, and physical factors such as specific energy
• Gasoline produces about 1.6 times more energy than ethanol by weight and 1.4 times more by volume
• Incomplete combustion of carbon-containing compounds like hydrocarbons can produce carbon monoxide, carbon, and soot
• Carbon monoxide is poisonous as it binds irreversibly to haemoglobin, while soot can damage lungs and the heart
• Photosynthesis is the process of converting carbon dioxide and water into carbohydrates in the presence of chlorophyll
• Coal was formed from plant material during the Carboniferous period, while crude oil was formed from marine organisms mainly during the Paleozic era
• Natural gas consists mainly of methane and may occur with coal or crude oil
• Fossil fuels like coal and oil contribute to acid rain due to the formation of sulphur dioxide during combustion
• Biofuels are renewable sources of energy that release stored energy through recent carbon fixation via photosynthesis
• Biofuels can be produced through direct combustion, biogas production, or fermentation to produce ethanol
• Ethanol can be combined with gasoline to produce a fuel called gasohol
• Hydrogen fuel cells convert chemical energy directly to electrical energy by reacting oxygen and hydrogen to produce water
• Hydrogen fuel cells do not pollute as water is the only product
• Methanol fuel cells produce carbon dioxide and water as products