Using the Earth's resources and sustainable development

Humans use the Earth’s resources to provide warmth, shelter, food and transport.

Natural resources, supplemented by agriculture, provide food, timber, clothing and fuels.

Finite resources from the Earth, oceans and atmosphere are processed to provide energy and materials.

Chemistry plays an important role in improving agricultural and industrial processes to provide new products and in sustainable development, which is development that meets the needs of current generations without compromising the ability of future generations to meet their own needs.

Students should be able to:
- state examples of natural products that are supplemented or replaced by agricultural and synthetic products
- distinguish between finite and renewable resources given appropriate information.

Students should be able to:
- extract and interpret information about resources from charts, graphs and tables
- use orders of magnitude to evaluate the significance of data.

Potable water

Water of appropriate quality is essential for life. For humans, drinking water should have sufficiently low levels of dissolved salts and microbes. Water that is safe to drink is called potable water. Potable water is not pure water in the chemical sense because it contains dissolved substances.

The methods used to produce potable water depend on available supplies of water and local conditions.

In the United Kingdom (UK), rain provides water with low levels of dissolved substances (fresh water) that collects in the ground and in lakes and rivers, and most potable water is produced by:
- choosing an appropriate source of fresh water
- passing the water through filter beds
- sterilising.

Sterilising agents used for potable water include chlorine, ozone or ultraviolet light.

If supplies of fresh water are limited, desalination of salty water or sea water may be required. Desalination can be done by distillation or by processes that use membranes such as reverse osmosis. These processes require large amounts of energy.

Students should be able to:
- distinguish between potable water and pure water
- describe the differences in treatment of ground water and salty water
- give reasons for the steps used to produce potable water.

Waste water treatment

Urban lifestyles and industrial processes produce large amounts of waste water that require treatment before being released into the environment. Sewage and agricultural waste water require removal of organic matter and harmful microbes. Industrial waste water may require removal of organic matter and harmful chemicals.

Sewage treatment includes:
- screening and grit removal
- sedimentation to produce sewage sludge and effluent
- anaerobic digestion of sewage sludge
- aerobic biological treatment of effluent.

Students should be able to comment on the relative ease of obtaining potable water from waste, ground and salt water.

Alternative methods of extracting metals

The Earth’s resources of metal ores are limited.

Copper ores are becoming scarce and new ways of extracting copper from low-grade ores include phytomining, and bioleaching. These methods avoid traditional mining methods of digging, moving and disposing of large amounts of rock.

Phytomining uses plants to absorb metal compounds. The plants are harvested and then burned to produce ash that contains metal compounds.

Bioleaching uses bacteria to produce leachate solutions that contain metal compounds.

The metal compounds can be processed to obtain the metal. For example, copper can be obtained from solutions of copper compounds by displacement using scrap iron or by electrolysis.

Students should be able to evaluate alternative biological methods of metal extraction, given appropriate information.