C10: WATER

Question 1

What is potable water?

Answer 1

water that is safe to drink

Question 2

What is pure water?

Answer 2

H2O only

Question 3

Where does rainwater collect?

Answer 3

-underground (‘ground water’)
-in lakes and rivers (‘freshwater’)

Question 4

How is freshwater treated to become potable water?

Answer 4

-passed through filter beds to remove solid particles
-sterilised to kill microorganisms using chlorine/UV light/ozone

Question 5

If fresh water supplies are limited what is the alternative?

Answer 5

desalinating sea water

Question 6

What are the 2 methods of desalinating sea water?

Answer 6

-distillation
-reverse osmosis

Question 7

Why is desalination rarely used?

Answer 7

it’s expensive and increases CO2 emissions as lots of energy is required

Question 8

What are the 5 stages of waste water treatment?

Answer 8

-screening (filtering)
-sedimentation
-biological treatment
-sludge treatment
-sterilisation

Question 9

What is the process of waste water treatment?

Answer 9

-SCREENING - to remove large solids
-SEDIMENTATION - solids sink to form sludge, liquid effluent remains above
-effluent aerobically digested in presence of O2 to remove organic matter and harmful microorganisms
(-effluent is then sterilised to produce potable water)
-sludge is anaerobically digested in the absence of O2 to produce biogas

Question 10

RP - Analysis and purification of water: method for analysing a sample of water

Answer 10

-use universal indicator paper to measure the pH the water sample
-accurately weigh an empty evaporating basin and record to 2dp
-pour 10cm^3 into the evaporating basin
-heat evaporating basin on a tripod and gauze using a Bunsen burner until the solids start to form and the water has evaporated
-after the evaporating basin has cooled, weigh it again and calculate the mass of the solids that were dissolved in the water by subtracting the mass of the empty evaporating basin from the mass of the evaporating basin with the solids

Question 11

RP - Analysis and purification of water: method for purifying a sample of water

Answer 11

-place the water sample in a conical flask and set up the apparatus for distillation
-heat water using Bunsen burner until it boils
-the distilled water will collect in the other boiling tube
-analyse distilled water with cobalt chloride paper