Purifying Water

Question 1

Where do we get water resource from in the UK?

Answer 1

Surface water -
lakes, rivers and reservoirs (artificial lakes)

Groundwater -
aquifers (rocks that trap water underground)

Question 2

How do you filter water ? (3 steps)

Answer 2

1. Filtration -
   wire mesh with gravel and sand beds - filter out solids
2. Sedimentation -
   Iron sulfate or aluminium sulfate added to the water - make particles clump at the bottom
3. Chlorination-
   Chlorine has bubbled through water and kill bacteria/microbes

Question 3

Why is water still dangerous after purifying it?

Answer 3

Some impurities cannot be filtered out which causes water hardness

• harmful chemicals such as pesticides and fertilisers found

Question 4

Why isn’t tap water 100% safe?

Answer 4

Many pollutants which come from:

• nitrate residues from fertilisers running off on lakes and rivers
  (If overdosed in human, can be harmful for babies, the nitrate stop blood from carrying oxygen)
• lead compounds from old lead pipes
  (Lead is poisonous)
• pesticide residues for spraying it too near to rivers and lakes

Question 5

What is another way to get pure water without filtering it?

Answer 5

Distilling water

Question 6

What is a disadvantage if distilling water?

Answer 6

Demands lots of energy, very expensive

Not suitable to produce large amount of fresh water

Question 7

How do water companies test their pollutant level in water?

Answer 7

Check for dissolved ions by using precipitation (a reaction where 2 dissolved compounds form an insoluble solid)

Question 8

How to test if sulfate ions are in water?

Answer 8

Using barium chloride - if a white precipitate occurs then there is sulfate ion In water

Question 9

How to test if halide ions are in water ?

Answer 9

Using silver nitrate

Question 10

Revise p72

4) reaction needed to know for exam

Answer 10

Chloride ions
Bromide ions
Iodine ions