Natural Sciences and Technology Grade 6 Term 3: Energy and Change Mains Electricity (ppt 2) Topic 4 Mains Electricity Fossil Fuels and electricity Natural Sciences and Technology - Grade 6 How fossil fuels were formed It came from living
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Presentation Transcript
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Natural Sciences and Technology Grade 6 Term 3: Energy and Change
Mains Electricity
(ppt 2)<br>
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Topic 4 Mains Electricity Fossil Fuels and electricity Natural Sciences and Technology - Grade 6<br>
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How fossil fuels were formed It came from living things (organisms) that died millions of years ago.
There were living things, forests, ferns and wetlands which can be referred to as living matter.
It died and formed different layers of sand and mud.
After being put under pressure for millions of years, it gradually changed into substances like oil and coal. Natural Sciences and Technology - Grade 6<br>
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A discovery... Natural Sciences and Technology - Grade 6<br>
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How fossil fuels are formed Natural Sciences and Technology - Grade 6<br>
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How fossil fuels are formed Natural Sciences and Technology - Grade 6<br>
Coal Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and hydrocarbons.
Coal is made of the remains of ancient trees and plants that grew in swampy jungles in climates that were moist and warm millions of years ago. Natural Sciences and Technology - Grade 6<br>
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Coal The energy in coal comes from the Sun’s energy [Plants used the sun’s energy to grow and for photosynthesis. The plant died and trapped the energy that was stored in its flowers, stems and leaves].
The physical and chemical process that the dead organisms underwent, became coal , known as carbonization. Natural Sciences and Technology - Grade 6<br>
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Coal Power stations use coal to produce electricity.
Coal-fired power stations use the energy from burning coal to heat water to steam in a boiler.
There are 20 coal-fired power stations in South Africa.
One of the biggest coal fired power stations in our country is Duvha [15 km east of Witbank in Mpumalanga Station; started in November 1975 and in operation from 1984; cost R1,6 billion to build]. Natural Sciences and Technology - Grade 6<br>
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Coal ranking If coal has undergone a longer carbonization period, it is ranked high and called anthracite.
If coal has not undergone too much carbonization, it is ranked low, and called peat.
If coal is formed from compressed peat, it is ranked the lowest , has a carbon content of 25 -35%, referred to as brown coal and called lignite. Natural Sciences and Technology - Grade 6<br>
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The diagram shows how coal is converted into electricity Natural Sciences and Technology - Grade 6<br>
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Process of coal being converted into electricity Coal is transported from the coal mine to the power station.
The coal is then milled into a very fine
powder [pulverised] which allows it to
burn quicker.
It is then blown into the boiler where it is burnt at a very high temperature. Natural Sciences and Technology - Grade 6<br>
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Process of coal being converted into electricity Heat and hot gases are produced and it converts
the water into steam.
High-pressure steam causes the turbine [big wheel] to turn.
The turbine is connected to the generator’s magnets and wire coils to produce energy.
Electric current is sent to the switchboard (transformer) where it gets regulated and then sent to the homes through on-land cables [power lines and substations]. Natural Sciences and Technology - Grade 6<br>
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Oil Oil is a thick liquid that can be used to make petrol.
The petrol is used in different vehicles, e.g. trucks, cars and buses.
It is found in reservoirs [underground areas at the bottom of the ocean floor and river beds].
The mud and the sand [silt] layers change into rock and traps the oil reservoirs.
It is a yellowish black liquid. Natural Sciences and Technology - Grade 6<br>
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Oil Offshore drills are oil drills that are mounted in the oceans.
The five top crude oil producers in the world are USA, China, Saudi Arabia, Iran and Russia.
Electricity is generated from crude oil
in the same manner as coal. Natural Sciences and Technology - Grade 6<br>
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Natural gas Natural Gas, in its purest form, is odourless, colourless and shapeless.
It differs from coal and oil, because it is clean when it burns and lower levels of harmful by-products are deposited into the air.
It is formed mostly from methane, but it can also be formed from pentane, butane, propane and ethane. Natural Sciences and Technology - Grade 6<br>
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Natural gas Methane is made up of one carbon atom and four hydrogen atoms.
Electricity is generated from natural gas in the same manner as coal and oil. Natural Sciences and Technology - Grade 6<br>
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How electricity gets to our homes [1] Natural Sciences and Technology - Grade 6<br>
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How electricity gets to our homes [2] Natural Sciences and Technology - Grade 6<br>
