Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Define the lithosphere and its importance.
• Describe the extraction of gold, platinum, and coal.
• Explain the environmental impacts of coal combustion.
• Distinguish between renewable and non-renewable energy.
• Discuss the impacts of mining in South Africa.

Lesson summary

South Africa's economy is heavily reliant on its mineral and energy resources, both for domestic use and export. Understanding the lithosphere – the Earth's rigid outer layer, encompassing the crust and the uppermost part of the mantle – is crucial to understanding where these resources come from and the chemical processes involved in their extraction and utilisation. This topic directly impacts our daily lives, from the electricity powering our homes to the fuel powering our vehicles and the materials used to build infrastructure.

Furthermore, understanding the environmental consequences of mining and energy production is vital for sustainable development and responsible citizenship.

Lesson notes

2.1 The Lithosphere as a Source of Minerals and Energy Resources: The lithosphere is a vast reservoir of chemical elements and compounds. These are concentrated in specific locations due to geological processes that have occurred over millions of years. Mining involves extracting these valuable minerals and metals from the Earth's crust. Energy resources, such as coal, are also found within the lithosphere and are essential for electricity generation and other industrial processes. 2.2 Major Mineral Resources in South Africa and Their Extraction: Gold: South Africa has historically been a major gold producer. Gold is often found in quartz veins and conglomerate rocks. Extraction typically involves underground mining or open-pit mining, depending on the depth and distribution of the ore. The gold is then extracted from the ore through processes like cyanide leaching.

Cyanide Leaching: This process involves dissolving gold in a cyanide solution. The gold cyanide complex is then recovered using zinc precipitation or activated carbon adsorption.

Reaction: `4Au(s) + 8CN−(aq) + O2(g) + 2H2O(l) → 4[Au(CN)2]−(aq) + 4OH−(aq)` This reaction shows how gold reacts with cyanide in the presence of oxygen and water to form a soluble gold cyanide complex.

Platinum Group Metals (PGMs): South Africa holds the world's largest reserves of PGMs, found mainly in the Bushveld Igneous Complex. These metals are extracted through underground mining, followed by complex metallurgical processes to separate the individual PGMs. Froth flotation is a key step.

Froth Flotation: This technique separates valuable minerals from waste rock (gangue) based on differences in their surface properties. Chemicals called collectors are added to selectively make the desired mineral hydrophobic (water-repelling). Air is then bubbled through the mixture, and the hydrophobic mineral particles attach to the air bubbles, forming a froth that is skimmed off.

Coal: Coal is a fossil fuel formed from the remains of ancient plants. South Africa has significant coal reserves, used primarily for electricity generation. Coal is typically extracted through surface mining (strip mining) or underground mining. 2.3 Coal Combustion and Environmental Impacts: Coal combustion is a chemical process that releases energy in the form of heat, which is used to generate electricity.

However, this process also releases harmful pollutants into the atmosphere.

Combustion Reaction (Simplified): `C(s) + O2(g) → CO2(g)` This is a simplified version and ignores impurities and incomplete combustion.

Formation of Acid Rain: Coal often contains sulfur. When burned, sulfur dioxide (SO2) is produced. SO2 reacts with water in the atmosphere to form sulfuric acid (H2SO4), a major component of acid rain. `S(s) + O2(g) → SO2(g)` `2SO2(g) + O2(g) → 2SO3(g)` `SO3(g) + H2O(l) → H2SO4(aq)` Greenhouse Gases: The combustion of coal releases carbon dioxide (CO2), a major greenhouse gas that contributes to global warming and climate change. 2.4 Renewable vs.

Non-renewable Energy Resources: Renewable Energy Resources: These resources are naturally replenished and can be used sustainably without depletion.

Examples include: Solar Energy: South Africa has abundant sunshine, making solar energy a promising renewable resource.

Wind Energy: Coastal areas and mountainous regions have good wind resources that can be harnessed by wind turbines.

Hydropower: Dams can be used to generate electricity from flowing water.

Biomass: Organic matter, such as wood and agricultural waste, can be burned for energy or converted into biofuels.

Non-renewable Energy Resources: These resources are finite and cannot be replenished on a human timescale.

Examples include: Coal: As discussed above.

Oil: A liquid fossil fuel used for transportation and other purposes.

Natural Gas: A gaseous fossil fuel used for heating and electricity generation.

Uranium: Used in nuclear power plants. 2.5 Environmental and Socio-economic Implications of Mining: Mining can have significant environmental and socio-economic impacts: Environmental Impacts: Habitat Destruction: Mining operations often require clearing large areas of land, destroying habitats.

Water Pollution: Mining can contaminate water sources with heavy metals and other pollutants.

Air Pollution: Dust and emissions from mining operations can pollute the air.

Soil Erosion: Mining can destabilize soils and lead to erosion.

Socio-economic Impacts: Job Creation: Mining can create jobs in local communities.

Economic Development: Mining can contribute to economic growth through exports and tax revenue.

Social Disruption: Mining can displace communities and disrupt social structures.

Health Problems: Exposure to dust and chemicals in mining areas can lead to health problems. Guided Practice (With Solutions)

Question 1: Write a balanced chemical equation for the complete combustion of methane (CH4), a component of natural gas.

Solution: Step 1: Identify the reactants and products.