using resources Flashcards
when are orders of magnitude calculations used?
when the exact number of something isn’t crucial and so we use a rough approximation of the quantity
when using orders of magnitude what to we round values to?
the closest power of 10
what do humans use resources for?
to provide warmth,shelter,food and transport
what does finite mean?
a finite resource can not be replaced as quickly as they are being used and so one day they will run out
give an example of a finite resource
fossil fuels-we use millions everyday but they form at a much slower rate
what does renewable mean?
a renewable resource can be replaced as quickly as they are used and will never run out
give an example of a renewable resource?
wood-trees can be grown at a rate similar to which we use them
what is potable water?
potable water is water that is safe to drink
what is the difference between potable water and pure water?
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
what is the 3 criteria that potable water needs to meet?
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
where is fresh surface water found from?(3)
lakes,rivers or reservoirs
what is fresh water?
fresh water is water that has a relatively low concentration of dissolved salts and other substances
where is ground water found?(2)
aquifers or permeable rock with trapped water
what is the benefit of using surface water to create potable water?(2)
-easy to access
-replaced frequently
one negative of using surface water to create potable water?
it can dry up in high temperatures
give step one for treating fresh water
first the fresh water is passed through a wire mesh to filter out any big undissolved solids like twigs
give step two for treating fresh water
next the water is passed through a bed of sand and gravel to filter out any smaller undissolved solids
give step 3 for treating fresh water
finally we sterilise the water by exposing it to either uv or ozone or we can bubble chlorine gas through it
