C14: The Earth's Resources

What is sustainable development?

Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs.

What are finite resources and what are key examples?

• Resources that are used up faster than they can be naturally replaced, meaning they will eventually run out.

• Examples include crude oil, metal ores, coal, natural gas, and limestone.

What are renewable resources and what are key examples?

• Resources that can be replaced at the same rate or faster than they are consumed.

• Examples include timber, solar energy, wind energy, fresh water, and bioethanol.

How can chemistry reduce the use of finite resources?

• Developing synthetic alternatives to natural products.

• Improving industrial processes to use catalysts that save energy.

• Recycling metals, glass, paper, and plastics to conserve raw materials.

What is potable water?

Water that is safe for humans to drink because it contains sufficiently low levels of dissolved salts and microbes.

Why is potable water not the same as pure water?

• Pure water contains only H2O molecules with no dissolved substances.

• Potable water contains small amounts of harmless dissolved minerals and salts.

How is potable water produced from fresh water sources like rivers lakes and aquifers?

• Pass raw water through wire mesh and filter beds of sand and gravel to remove insoluble suspended solids.

• Sterilise the filtered water using chlorine, ozone, or ultraviolet light to kill harmful microorganisms and bacteria.

How is potable water produced from salty sea water by desalination?

• Processed using distillation where water is boiled to evaporate H2O away from dissolved salts and condensed.

• Processed using reverse osmosis where sea water is passed through a semi-permeable membrane under high pressure to separate salts.

• Both methods require huge amounts of energy, making desalination very expensive.

What are the main stages of waste water treatment?

• Screening to remove large solid objects like rags and plastic debris.

• Sedimentation in a settlement tank where heavy sludge sinks to the bottom and liquid effluent floats on top.

• Aerobic biological digestion of liquid effluent by bubbling air through it so bacteria break down organic matter.

• Anaerobic biological digestion of solid sludge by bacteria in sealed tanks to produce biogas and fertilizer.

Why is sewage treatment necessary before releasing water back into the environment?

Removes organic matter, toxic chemicals, and dangerous pathogens that would pollute ecosystems and spread disease.

Why are traditional copper extraction methods becoming unsustainable?

High-grade copper ores are running out, so new biological methods must be used to extract copper efficiently from low-grade ores.

How does phytomining work to extract copper?

• Plants are grown on soil containing low-grade copper ores and absorb copper ions through their roots.

• Plants are harvested, dried, and burned in a furnace to produce ash rich in copper compounds.

• Copper compounds are dissolved in sulfuric acid to produce a copper sulfate solution, which is extracted by electrolysis or displacement with scrap iron.

How does bioleaching work to extract copper?

• Bacteria are fed on low-grade copper ores to produce a solution of copper compounds called a leachate.

• Copper metal is extracted from the leachate solution using electrolysis or displacement with cheap scrap iron.

What are the advantages and disadvantages of phytomining and bioleaching?

• Advantages include conserving high-grade ores, requiring less energy than traditional mining, and causing minimal damage to the landscape.

• Disadvantages are that both processes are very slow and produce smaller yields of metal compared to traditional smeltin