Chemistry GCSE - using resources

Potable water

Safe to drink

Not pure

Low levels of salts and microbes

pH between 6.5-8.5

No micro organisms

Process of obtaining potable water from fresh water

Screening through wire mesh to remove large solids

Filtration through bed of sand and gravel to remove any smaller particles

Sterilisation by either exposure to ozone, use of UV light, or bubbling chlorine gas

Two processes of desalination

Distillation - salty water is heated to evaporate then condensed and collected.

Reverse osmosis - salty water is forced under pressure through a membrane which only allows water molecules through.

Both produce pure water

What needs to be removed from sewage and agricultural waste

Organic matter - can cause eutrophication

Harmful microbes - can cause disease

Harmful chemicals - can poison ecosystems or cause eutrophication

Eutrophication

When water becomes overly enriched with nitrogen and phosphorus which accelerates growth of algae

Process to treat waste water

Screening and grit removal by passing sewage through a screen

Sedimentation to produce sewage sludge and effluent allows small solid particules to sink to bottom of tank whilst liquid remains above

Anaerobic digestion of sludge by microorganisms in the absence of oxygen

Aerobic digestion of effluent by microorganisms in presence of oxygen. Removes organic. Matter and microbes.

What happens to sewage effluent when it has been aerobically digested

It can be released into environment for further treatment

What happens to sewage sludge once it has been anaerobically digested

Digestion produced biogas used to make electricity. Dried sludge can be used to make fertiliser

Clay ceramics

Dug out of ground, moulded and fired.

Brittle, stiff, insulator of heat and electricity

Glass

Heating limestone, sand and sodium carbonate, then cooled

Composites

Materials embedded in another. Made out of matrix and reinforcement.

Polymers

Large molecules formed when small ones join.

Mostly insulators, flexible, easily moulded

Metals

Extracted.

Malleable, conductors of heat and electricity, ductile, still, shiny, sonorous

What is the order of reactivity for metals

Please stop literally calling my African crazy zebra in to lab help class silly guys please

Potassium

Sodium

Lithium

Calcium

Magnesium

Aluminium

(Carbon)

Zinc

Iron

Tin

(Hydrogen)

Copper

Silver

Gold

Platinum

Bioleaching

Using bacteria that can live off the energy released when the carbon and sulfur bonds are broken to extract metal from low grade ores.

Phytomining

Plants will naturally absorb compounds containing metal ions from the soil through their roots system. The plant is then burned, releasing water vapour and carbon dioxide, leaving behind the ash containing the ore. The metal left is not pure and will have to go through electrolysis

Advantages of phytomining

Uses low grade ore

Requires less energy than smelting

Produces less air pollution

Reduces amount of waste rock

Disadvantages of phytomining

Can produce toxic chemicals

Much slower process

Electrolysis requires lots of electricity

Releases greenhouse gases

Advantages of bioleaching

Doesn’t release greenhouse gases

Can be used to extract low grade ores

Doesn’t require much energy

Very economical, simple and clean

Disadvantages of bioleaching

Produces toxic chemicals

Much slower

Not efficient

Produces lots of waste