GR11 Support pack for Chemical systems

Study & Master Support Pack | Grade 11 CAPS Physical Sciences Chemical systems This support pack for the Chemical systems strand of the Physical Sciences Grade 11 CAPS curriculum provides revision summaries on the topic to help prepare for the examinations. Learners can work through these individually at home or these could form the basis of a catch-up class or online lesson. You have permission to print or photocopy this document or distribute it electronically via email or WhatsApp. Cambridge University Press Africa is a proudly South African publisher. For more information on our Study & Master CAPS-approved textbooks and valuable resource materials, visit www.cambridge.org Brighter thinking I Better learning www.cambridge.org

Unit 1: Exploiting the lithosphere Summary • The lithosphere is a solid outer part of the Earth consisting of the crust and upper mantle. • Ores are rocks from which metals can be produced economically. • The ore body is that part of a mineral deposit where the ore minerals are concentrated into economically extractable amounts. • Non-renewable resources are natural resources that are limited and can be used up. • The reserve of a mineral is the total amount of a certain mineral in an area that can be exploited. • Mining is the action of digging into the lithosphere to collect valuable minerals. • Pre-treatment includes processes used to extract the minerals from the rock, e.g. size reduction, separation and roasting. • Reduction refers to when the metal ions in minerals are reduced, mostly by using carbon, to yield free metal. • The most important gold mining region in South Africa is the Witwatersrand basin. • Gold ore is mined, crushed and then extracted through cyanidation or zinc precipitation. • Acid rain forms when oxides of sulfur and nitrogen dissolve in rainwater. • Air pollution is caused by pollutants that damage the health of animals, plants and humans. • The greenhouse effect is the process by which radiation from the atmosphere warms the Earth’s surface to support life. • Global warming is the gradual increase in the overall temperature of the Earth’s atmosphere as a result of increased levels of CO2 and other pollutants in the atmosphere. 54 S T U DY & M A S T E R P H Y S I C A L S C I E N C E S S U P P O R T PA C K G R A D E 1 1

Revision exercises: Unit 1 – Exploiting the lithosphere 1. Give one term for the following descriptions. The majority of the common minerals in Earth’s crust can be classified into seven a) The process by which commercially groups, according to their chemical composi- valuable mineral resources are removed tion. This classification is summarised in the from the Earth’s surface table below. b) The gas formed when calcium carbonate is heated Name of Example Chemical c) Mineral deposits that can be extracted mineral group composition profitably Carbonate Calcite CaCO3 d) Corrosion of iron Halide Halite NaCl e) Piles of crushed or ground-waste rock Oxide Haematite Fe2O3 produced as a by-product of mineral Sulfide Galena PbS processing Sulfate Gypsum CaSO4 f) The outflow of acidic water, rich in heavy Silicate Quartz SiO2 metals, from metal and coal mines g) Digging a large hole to remove ore Native element Gold Au h) The type of chemical reaction that usually occurs when a metal is extracted from c) Explain the meaning of the term ‘mineral’. its ore d) How does a native element compare to the i) The gases surrounding Earth other minerals? j) A broad prehistoric time period during e) Which element forms part of most mineral which humans widely used stone for groups? tool making f) Bauxite (Al2O3·2H2O) and clay (Al2O3·2SiO2·H2O) are both minerals 2. The chart shows the relative abundance of of aluminium. Why is bauxite called some of the elements in Earth’s crust. aluminium ore, but not clay? iron 4,7% aluminium 7,5% 3. Africa is often portrayed as a continent that emits little carbon dioxide yet stands to suffer calcium the effects of the developed world’s pollution. 3,4% This view only holds if South Africa is other excluded. We are the world’s seventh largest oxygen 9,2% 49,5% coal producer and thirteenth-largest CO2 emitter, with per-capita emissions twice the silicon 25,7% global average. But South Africa is also blessed with abundant renewable energy resources. In 2012, the government began inviting private investors to produce cleaner electricity for the national grid. However, a) What is the most common element in the government also plans to increase coal Earth’s crust? exports and the production of electricity from b) Which metallic element is the most coal. Eskom is currently building the third- common? and fourth-largest coal-fired power plants in the world. CHEMICAL SYSTEMS 55

Waterberg BOTSWANA coalfield Central Johannesburg Basin SWAZILAND coalfield Richard’s LESOTHO Bay coal terminal a) What is the main reason for South Africa’s high CO2 emissions? b) Global warming is caused by high emissions of CO2 worldwide. i) Briefly explain the difference between the greenhouse effect and global warming. ii) Global warming is slowly changing the world’s climate. How will South Africa be affected? c) South Africa is blessed with abundant renewable energy resources. Name the two most important and abundant sources. d) What is meant by renewable energy sources? e) To provide enough coal to all the power stations more and more coal mines are opened. i) Where in South Africa are the richest coal fields? Use the map to answer the question. ii) Coal mines have enormous negative impacts on farming as well as the environment. Discuss these impacts. 56 S T U DY & M A S T E R P H Y S I C A L S C I E N C E S S U P P O R T PA C K G R A D E 1 1

Unit 1: Answers 1. a) Mining d) Energy sources that capture their energy b) Carbon dioxide from on-going natural processes, such as c) Ores sunshine, wind and moving water d) Rust e) i) In the Highveld area, east of e) Tailings Johannesburg f) Acid mine drainage ii) The Highveld area in Mpumalanga is g) Opencast mining excellent farmland. At the current rate h) Reduction of coal mining in this area, hundreds i) Atmosphere of thousands of acres will be lost for j) Stone age farming. Some important rivers are so polluted by acid mine drainage, which 2. a) Oxygen seeps out of abandoned mines, that b) Aluminium they can no longer be used by farms c) Minerals are inorganic, crystalline solids or factories. that occur naturally in the lithosphere, and they are pure (either an element or a compound). d) A native element, like gold, can be found uncombined in Earth’s crust. e) Oxygen f) Bauxite contains enough aluminium to make it economically worthwhile to mine. 3. a) Approximately 94% of the country’s electricity is generated by coal-fired power stations. Burning coal releases tons of CO2 each year. b) i) The greenhouse effect refers to the retention of heat in the atmosphere by greenhouse gases. Due to increasing levels of greenhouse gases in the atmosphere, partially as a result of human and industrial activity, progressively more heat is being trapped, resulting in a phenomenon commonly referred to as global warming. ii) Rise in temperatures. Shifting of rainfall patterns – western parts of South Africa will become drier. There will be an increase in the frequency and severity of extreme weather events. c) Wind energy and solar energy CHEMICAL SYSTEMS 57