Chemistry_Grade_10-12 (1).pdf

While most of south africas oil is imported and then

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While most of South Africa’s oil is imported and then processed at a refinery in either Durban, Cape Town or Sasolburg, some is extracted from coal, as discussed in section 21.8. 21.9.3 Other oil products Oil can also be used to make a variety of different products. You will find more information on this in chapter 23. Fractional distillation Fractional distillation is the separation of a mixture into the parts that make it up. In oil refineries, crude oil is separated into useful products such as asphalt, diesel, fuel oil, gasoline, kerosine, liquid petroleum gas (LPG) and tar, to name just a few. Cracking There are two types of cracking, steam cracking and hydrocracking . Cracking is used to change heavy hydrocarbons such as petroleum into lighter hydrocarbons such as fuels (LPG and gasoline), plastics (ethylene) and other products that are needed to make fuel gas (propylene). 21.9.4 The environmental impacts of oil extraction and use Some of the key environmental impacts associated with the extraction and use of oil are as follows: Pollution Exploring the oceans for oil, and the actual drilling process, can result in major pollution. Ecosystem impacts Dredging the ocean floors for oil can disrupt seabed ecosystems. Global warming Burning oil as a fuel source produces carbon dioxide, which contributes towards global warming. 21.10 Alternative energy resources As the world’s population increases, so does the demand for energy. As we have already men- tioned, many of our energy resources are non-renewable and will soon run out. In addition, many of the fuels that we use produce large amounts of greenhouse gases, which can contribute towards global warming. If we are to maintain the quality and health of our planet, and also meet our growing need for energy, we will need to investigate alternative energy resources. In this next section, we are going to take a closer look at some of these possible alternatives. Many of these options are very controversial, and may have both pros and cons. Nuclear power Another element that is found in the crust, and which helps to meet our energy needs, is uranium . Uranium produces energy through the process of nuclear fission (chapter ?? ). Neutrons are aimed at the nucleii of the uranium atoms in order to split them. When the nucleus of a uranium atom is split, a large amount of energy is released as heat. This heat is used to produce steam, which turns turbines to generate electricity. Uranium is 415
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21.10 CHAPTER 21. THE LITHOSPHERE - GRADE 11 produced as a by-product of gold in some mines in the Witwatersrand, and as a by-product in some copper mines, for example in Palaborwa. Many people regard this type of nuclear power as relatively environmentally friendly because it doesn’t produce a lot of greenhouse gases. However, generating nuclear power does produce radioactive wastes, which must be carefully disposed of in order to prevent contamination. There are also concerns around leaking of nuclear materials.
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