C12 - Pure And Impure Substances

Question 1

Disadvantages of distillation

Answer 1

• large amounts of energy - expensive

Question 2

How can you obtain potable water? (process)

Answer 2

• passed through filter beds to removed solids
• made of sand and gravel
• settlement tank - sand and soil settle out
• aluminium sulfate and lime are added
• chlorine and ozone is added/ultra violet is passed through to sterilise the water (reduces microbes)

Question 3

Treating waste water (process)

Answer 3

• screening - remove large solid objects and grit
sewage passes through metal grid trapping large objects
• primary treatment - solid sediments settle, sludge pushed to centre
• effluent flows into next tank
• secondary treatment - aerobic digestion, useful bacteria feed on microbes and break them down aerobically
• tank is aerated by bubbling air through waste water
• final treatment - treated waste water is discharged back into rivers