Chemistry_Grade_10-12 (1).pdf

There are alternative energy sources available but

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There are alternative energy sources available, but they will take years to become functional, and many of them have their own problems. Another way to look at the problem, is to put the focus on reducing how much energy is used rather than focusing only on ways to meet the growing demand. 416
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CHAPTER 21. THE LITHOSPHERE - GRADE 11 21.11 1. In your groups, discuss ways that each of the following groups of people could save energy. (a) industries (b) domestic users (c) farmers 2. Discuss creative incentives that could be used to encourage each of these groups to reduce their energy consumption. 21.11 Summary The lithosphere is the solid, outermost part of our planet and contains many important metal elements such as gold and iron, as well as products that are needed to produce energy. These elements are seldom found in their pure form, but rather as minerals in rocks . A mineral is formed through geological processes. It can either be a pure element (e.g. gold) or may consist of a number of different elements e.g. the gold-bearing mineral calaverite (AuTe 2 ). A rock is an aggregate of a number of different minerals. An ore is rock that contains minerals which make it valuable for mining. Minerals have been used throughout history . As new metals and minerals were discovered, important growth took place in industry, agriculture and technology. Gold is one of the most important metals in the history of South Africa. It was the discovery of gold that led to an influx of fortune-seeking foreigners, and a growth in mining villages and towns. Most of South Africa’s gold is concentrated in the ’Golden Arc’ in the area between Johannesburg and Welkom. Three methods are used to obtain gold from the lithosphere: panning , open cast mining and shaft mining . Gold ore must be processed so that the metal can be removed. One way to process the ore after it has been crushed is a method called gold cyanidation . A cyanide solution is added to the crushed ore so that a gold-cyanide solution is formed. Zinc is then added to this solution so that the gold is precipitated out. Gold has a number of important characteristics which make it a useful metal for jewelery and other applications. The metal is shiny, durable, malleable, ductile, is a good conductor of electricity and is also a good heat reflector. Gold mining has a number of environmental impacts , which include resource consump- tion, air pollution, poisoned water, solid waste and the destruction of biodiversity in natural areas. Mine rehabilitation is one way of restoring old mine sites to what they were like before. Iron is another important metal and is used in industry, furniture and building materials. Iron is usually found in minerals such as iron oxides . These minerals must be processed to remove the metal.
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