Unit 5a chemistry

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Unit 5a - Fuels

Oil is the source of many fuels and this section deals with their uses. Pollution resulting from burning these fuels is also considered.

Energy in Everyday Life

Energy is used to provide electricity, heating, lighting and cooking for homes as well as the power necessary to allow industry to function.

Burning Substances

Burning is a chemical reaction, to combine with oxygen, in which energy (mainly heat) is released - this kind of reaction is called an exothermic reaction.
Combustion is another word for burning. A fuel is a substance which burns in oxygen giving out heat.
The opposite of an exothermic reaction is an endothermic reaction 0 one in which energy is taken in during the reaction.

A Chemical Reaction

Air is a mixture of gases. The two main gases in air are oxygen (O2) and Nitrogen (N2).
Oxygen - 20% , Nitrogen - 80%.
Oxygen reacts with a fuel when it burns.
Oxygen relights a glowing splint.
Your breath contains oxygen which helps things to burn.
The safest way to put out a chip pan is to cover it with a damp cloth to stop oxygen getting at the fire.
For a substance to burn, heat and oxygen is required (i.e. for a fire you need heat, oxygen and a fuel).
The test for the presence of oxygen: 
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Oxygen gas is produced when potassium permanganate is heated.

Fossil Fuels

A fossil fuel is a fuel which has been made under the earth from natural living things millions of years ago.
Extreme heat and pressure turn them into fossil fuels.
In the beginning their energy came from the sun. Example of fossil fuels are coal, oil and natural gas.
Coal) Coal is called a fossil fuel because it was formed from the remains of vegetation that grew as long as 400 million years ago. The plants that formed coal captured energy from the sun through photosynthesis to create the compounds that make up plant tissues. The most important element in the plant is carbon, which gives coal most of its energy.
Natural Gas) Natural Gas is found within the ground, it contains methane, ethane, propane, butane, pentane and traces of hexane and heptanes.
Oil) Oil is commonly formed in rock or in sealed pockets under the sea bed. It is formed from plant and animal matter that has broken down and been subjected to extremes of temperature and pressure over millions of years.

Burning Fossil Fuels) the burning of fossil fuels releases the sun's energy from things which had been living millions of years ago.

Fossil Fuel + O2 --> CO2 + H2O +Energy (containing C + H). 

A Limit to Energy Sources

Conservation of fuels simply means to try to use as little as possible to save remaining stocks.
It is important to conserve our resources of coal, oil and gas as some day they will run out.
Alternative sources to these fuels are - nuclear, tidal/wave,

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