using resources

Question 1

when are orders of magnitude calculations used?

Answer 1

when the exact number of something isn’t crucial and so we use a rough approximation of the quantity

Question 2

when using orders of magnitude what to we round values to?

Answer 2

the closest power of 10

Question 3

what do humans use resources for?

Answer 3

to provide warmth,shelter,food and transport

Question 4

what does finite mean?

Answer 4

a finite resource can not be replaced as quickly as they are being used and so one day they will run out

Question 5

give an example of a finite resource

Answer 5

fossil fuels-we use millions everyday but they form at a much slower rate

Question 6

what does renewable mean?

Answer 6

a renewable resource can be replaced as quickly as they are used and will never run out

Question 7

give an example of a renewable resource?

Answer 7

wood-trees can be grown at a rate similar to which we use them

Question 8

what is potable water?

Answer 8

potable water is water that is safe to drink

Question 9

what is the difference between potable water and pure water?

Answer 9

pure water contains only h20 molecules making it unsafe to drink whereas potable water contains small amounts of dissolved substances making it impure and safe to drink

Question 10

what is the 3 criteria that potable water needs to meet?

Answer 10

1.levels of undissolved solids need to be fairly low
2.it needs to have a ph between 6.5 and 8.5
3.it must contain no microorganisms eg bacteria or fungi

Question 11

where is fresh surface water found from?(3)

Answer 11

lakes,rivers or reservoirs

Question 12

what is fresh water?

Answer 12

fresh water is water that has a relatively low concentration of dissolved salts and other substances

Question 13

where is ground water found?(2)

Answer 13

aquifers or permeable rock with trapped water

Question 14

what is the benefit of using surface water to create potable water?(2)

Answer 14

-easy to access
-replaced frequently

Question 15

one negative of using surface water to create potable water?

Answer 15

it can dry up in high temperatures

Question 16

give step one for treating fresh water

Answer 16

first the fresh water is passed through a wire mesh to filter out any big undissolved solids like twigs

Question 17

give step two for treating fresh water

Answer 17

next the water is passed through a bed of sand and gravel to filter out any smaller undissolved solids

Question 18

give step 3 for treating fresh water

Answer 18

finally we sterilise the water by exposing it to either uv or ozone or we can bubble chlorine gas through it

Question 19

what is desalination?

Answer 19

desalination is a method to extract potable water from sea water

Question 20

what is a disadvantage of using desalination for a water source?

Answer 20

it requires loads of energy to boil the water making it very expensive

Question 21

what two ways can water be desalinated?

Answer 21

by distillation or reverse osmosis

Question 22

give the method for desalination by distillation (3 steps)

Answer 22

1.boil the salty water-this will begin to evaporate into the tube
2.now the water vapour will cool in a condenser and drip into a beaker
3.the pure water has condensed and is now in the beaker while the salt is left behind

Question 23

give the method for reverse osmosis (3 steps)

Answer 23

1.salty water is passed through a membrane which only allows the water molecules to pass through
2.all of the ions and larger molecules get trapped and separated from the water
3.this will give us pure distilled water

Question 24

what are the three sources of waste water?

Answer 24

-domestic(showers,toilets,sinks)
-agricultural systems( nutrient run off,animal waste)
-industrial(chemicals)

Question 25

what do we have to do with waste water before we dispose of it?

Answer 25

treat it so it doesn't harm the environment

Question 26

what is stage one of sewage treatment?

Answer 26

screening the sewage 1.first we remove any large undissolved substances from the sewage such as plastic by passing the sewage through a mesh

Question 27

what is stage two of sewage treatment?

Answer 27

let the sewage sit in a settlement tank 1.this will allow the sewage to undergo sedimentation,in which the heavier solid bits will sink to the bottom to form sludge 2.will be left with effluent at the top 3.next the effluent and the sludge will be separated into two different tanks-

Question 28

what is stage 3 of sewage treatment?

Answer 28

break down all the organic matter 1.the sewage will now be broken down by biological breakdown through microorganisms 2.the microbes in the effluent tank will break this down through aerobic digestion 3.the organic matter in the sludge will be broken down by anaerobic digestion

Question 29

what is the final stage of sewage treatment?

Answer 29

1.the effluent will now be safe and released back into the environment 2.the anaerobic digestion of the sludge will produce methane which will be captured and used as an energy source while the remaining digested waste can be used as fertiliser