Using the Earth's Resources Flashcards
what has chemistry replace natural resources with?
a synthetic alternative
an example of a synthetic alternative?
rubber
where does natural rubber come from?
the sap of a tree
how is synthetic rubber produced?
using crude oil
examples of finite resources?
- fossil fuels
- metal
example of renewable resources?
wood
why is it important that human activities are sustainable?
so that we can meet our needs without preventing future generations from meeting theirs
what do artificial fertilisers do?
they allow us to grow more food with the land available
define potable water
water that is safe to drink
what’s the difference between potable water and pure water?
- pure water doesn’t contain any dissolved substances at all whilst potable water does contain dissolved substances
how is potable water produced? (3)
- choose a good source of fresh water
e.g lake or reservoir - pass the water through filter beds to remove leaves and suspended particles
- the water is then sterilised to kill microbes; in the uk, we use chlorine to sterilise potable water
how is potable water produced in countries that don’t have many sources of fresh water?
through desalination
what is desalination?
reduces the levels of dissolved minerals down to an acceptable level for potable water
two ways of carrying out desalination
- distillation
- reverse osmosis
why must waste water be carefully treated before going back into the environment? (2)
- because it contains a very large amount of organic molecules
e.g from urine or faeces - it also contains harmful microorganisms such as bacteria
what is the method in which waste water is treated? (7)
- in the first stage, the sewage is screened by passing through a mesh; this removes solids and pieces of grit
- then, the sewage is allowed to settle in large sedimentation tanks; this produces a liquid effluent and a semi-solid sludge which sinks
- the liquid effluent has air bubbled through it which allows aerobic bacteria to multiply
- the aerobic bacteria digest the organic molecules and harmful microorganisms
- after this, the liquid effluent can be safely discharged into a nearby river
- this sludge is then taken away and digested by anaerobic bacteria
- at the end, the digested sludge can be used as fertilisers for farming
what is the easiest way to produce potable water?
by using ground water from aquifers
- this is usually safe to drink, once it’s been
treated with chlorine
why would the water from aquifers need to be tested carefully?
because it can sometimes be polluted with things like fertilisers from farms
describe the process of desalination (4)
- pressure is applied to sea or salt water
- water molecules are forced over a partially permeable membrane
- salt molecules within the water are too big to pass through the membrane
- after the molecules of water have passed through the membrane, fresh water is created.
why is desalination expensive?
because it requires a lot of energy
state the three ways that water can be sterilised
- adding chlorine
- adding ozone
- adding UV (ultraviolet light)
metal extraction is by: (2)
-
reduction with carbon
- carbon removes impurities like the oxygen
from the metal ore
- carbon removes impurities like the oxygen
-
electrolysis
- an electric current separates the ions in
the ore to be left with a pure metal
- an electric current separates the ions in
define low-grade ore
ores that contain limited copper/only a very small amount of copper
why is copper now having to be produced from low-grade ores?
because copper ores are starting to become scarce
name the two methods in which copper is extracted from low-grade ores:
- phytomining
- bioleaching
define phytomining
the extraction of copper using plants
define bioleaching
the extraction of copper using bacteria
describe the process for phytomining (3)
- plants are burnt
- when this happens, the copper ions combine with oxygen to form copper compounds in the left over ash
- electrolysis is then used to purify the copper compounds
describe the process for bioleaching (3)
- the bacteria absorb the copper compounds
- they produce a leachate solution containing copper
- this leachate is then processed to remove the copper
what are the advantages (2) and disadvantages (1) of phytomining?
ADVANTAGES
- removes carbon dioxide via photosynthesis
- extracts copper from where there is limited resources
DISADVANTAGES
- burning releases carbon dioxide into the atmosphere
what are the advantages (3) and disadvantages (3) of bioleaching?
ADVANTAGES
- naturally occurring process
- reduces sulfuric acid from being released into the soil
- extracts from low grade-ores (where there’s little resources)
DISADVANTAGES
- costly; requires energy
- still needs electrolysis
- lengthy process
define what is meant by life-cycle assessment
looking at the environmental impact at each stage in a products life
what are the four main stages that need to be looked at when carrying out a life-cycle assessment?
- extraction and process of raw materials
- manufacturing and packaging
- use and reuse
- disposal
how are plastic bags produced?
using chemicals from crude oil
how are paper bags produced?
using wood from trees
name the disadvantages in the process of producing plastic bags? (2)
- extracting crude oil can be harmful to habitats if there’s an oil leak
- needs to be chemically processed which requires a lot of energy and releases waste products
name the disadvantages in the process of producing paper bags (3)
- felling trees for food is extremely destructive to habitats
- need to be chemically processed with requires a lot of energy and releases waste products
- making the paper requires large amounts of water
describe the differences between the use and reuse of paper and plastic bags: (4)
PAPER
- not very strong and tend to tear
- they’re often used once before being thrown away
PLASTIC
- plastic shopping bags are relatively strong
- they are often reused
describe the differences between the disposal of paper and plastic bags:
PAPER
- breaks down quickly, especially when wet
PLASTIC
- non biodegradable, meaning they can’t be broken down by microorganisms, and so they stay in the environment for a long time
