Ch14 The Earth's resources Flashcards
Potable water
water that is safe to drink
contains useful dissolved substances(not pure)
Obtaining fresh water
Rainwater falls to the ground
replenishes water in rivers and lakes
also seeps through soil and rocks to underground sources(aquifers)
can be obtained from porous rocks by drilling a pipe to form a water well
Forming potable water
- choose an appropriate source of fresh water
- pass the water through filter beds made of sand and gravel to remove solid particles
- a. sterilise the water by adding chemical agents such as chlorine or ozone, killing microorganisms
b. sterilise the water by passing ultraviolet light through the water, killing microorganisms
Desalination methods
- distillation
2. reverse osmosis
Advantages of distillation
under reduced pressure, water boils below 100°C (flash distillation) saving energy costs
Disadvantages of distillation
expensive
takes lots of energy
Reverse osmosis
Water is put under high pressure and passed through a partially permeable membrane
-has tiny pores (holes) in it, allowing water molecules through, but preventing most ions and molecules
Advantages of reverse osmosis
No heating involved, so it uses less energy than distillation
removes 98% of dissolved salts
Disadvantages of reverse osmosis
corrosion of pumps by salty water
lots of energy is needed to pressurise the water passing through
Finite resources
Those being used at a faster rate than they can be replaced
Examples of finite resources
fossil fuels
nuclear fuels
metal ores
limestone
Renewable resources
Those that can be replaced at the same rate at which they are used up
Examples of renewable resources
crops used to make biofuels
wind
water
Sustainable development
development that meets the needs of current
generations without compromising the ability of future generations
to meet their own needs
Examples of using lower amounts of finite resources
catalysts reduce the amount of energy required for certain industrial processes
man-made polymers can replace rubber extracted from tree sap
Sewage treatment
- screening - removing large solid objects and grit
- sedimentation to produce sewage sludge and effluent
- aerobic biological treatment of effluent
- useful bacteria feed on any remaining organic matter and harmful microorganisms - can be sterilised by ultraviolet light or chlorine, then discharged back into rivers
- anaerobic digestion of sewage sludge in high temperatures
- sewage dries, producing fertiliser, biogas or biofuel
Extracting copper metal from copper-rich ores
- sulfuric acid is used to produce copper sulphate solution
2. smelting - copper ore is heated to a high temp in a furnace with air to produce impure copper
Making pure copper from impure copper
- electrolysis
2. copper can be displaced from copper sulphate by iron
Bioleaching
bacteria feed on low-grade metal ores
produces acidic leachate solution containing copper(II) ions
Phytomining
plants absorb copper ions when growing on soil containing low-grade copper ore
plants are harvested and then burned to produce ash that contains copper compounds
copper ions are then leached/dissolved from the ash by adding sulfuric acid to make copper sulphate
Life cycle assessments
used to assess the impact on the environment caused by:
1. extracting and processing the raw materials
2. manufacturing and packaging
3. using, reusing and maintaining the product
during its lifetime
4. disposal of the product at the end of its useful life, including transport and
distribution at each stage
Extracting raw materials impact on the environment
using up limited resources such as ores and crude oil
damaging habitats through quarrying, mining, or felling trees
Manufacturing impact on the environment
using up land for factories
the use of machines and people
Disposal impact on the environment
using up land for landfill sites
whether any or all of the product can be recycled or reused
