C9 and C10 - Final Mocks

L1 - History of Our Atmosphere

Theory: A well-substantiated explanation of some aspect of the natural world based on a body of facts that have been repeatedly confirmed through experiment.

Early:

  • Mostly CO2
  • Small amounts of nitrogen
  • Gasses were produced through volcanic activity
  • Water vapour condensed as the Earth cooled to form oceans.
  • CO2 dissolved into the oceans, forming a weak acid that reacted with minerals to form carbonate rock. Some of this CO2 formed muscles and corals.

Oxygen levels began to increase in the Earth's atmosphere as photosynthetic algae developed.

L2 - Fossil Fuels

Natural gas is largely methane, it is mainly found near oil deposits as it is formed from plankton.

Coal is formed from the remains of fern and trees that die in wet marshlands. Here they do not decompose and are covered with sedimentary rock under great temperatures and pressures.

Crude oil is formed when plankton from the sea settles in mud on the seabed.

L3 - Carbon Footprint and Pollutants

Oxides of nitrogen are produced through combustion in car engines, this is a result of high temperatures.

Ways to reduce carbon footprint:

  • Insulating out homes
  • Using public transport
  • Renewable sources of energy used
  • Energy saving appliances
  • Eating less beef and dairy (methane reduction)
  • Trapping emitted methane from landfills and burning it to generate electricity.

L1 - Using Resources

Sustainable: The state of being able to meet out needs without preventing future generations from meeting theirs.

L2 - Potable Water

Drinking water has to have sufficiently low levels of dissolved salts and it cannot have high levels of microbes such as bacteria.

In the UK, rainwater provides most of our potable water because it contains low levels of dissolved salts. This water collects in aquifers, rivers, lakes and reservoirs. This water is:

  • Passed through water beds to remove matter such as leaves or suspended particles.
  • Sterilised to kill any microbes. We use chlorine for this in the UK.

Sea water has very high levels of dissolved substances so this water is made potable through desalination. This:

  • Reduces the levels of dissolved minerals.
  • This may be done through distillation or reverse osmosis.
  • Both processes require large amounts of energy which makes them very expensive.

L3 - Water Practical

To test for purity:

  • Check pH using a pH probe or universal indicator paper.
  • Place an empty evaporating basin on an electronic balance, record this mass.
  • Fill the evaporating basin with the water sample and place it on a tripod and gauze above a Bunsen burner.
  • Gently heat the water to allow it to cool.
  • Weigh the evaporating basin again, if its mass has increased then the water contained dissolved mineral ions.
  • The water may still contain dissolved gasses.

L4 - Waste Water Treatment

Waste water can contain organic matter from faeces and urine as well as microbes such as bacteria.

  • It must first be screened by passing through a mesh (removes solids and pieces of grit).
  • It is then left to settle in large sedimentation tanks; this produces a liquid effluent and a semi-solid sludge that sinks.
  • The sludge is taken away and digested by anaerobic bacteria (producing biogas). The digested sludge can be used for fertilisers.
  • Air is bubbled through the liquid effluent, allowing aerobic bacteria to multiply (these bacteria digest the organic molecules and harmful microorganisms).

Aquifers can sometimes be polluted with fertilisers.

L5 - Alternative Methods of Extraction

A metal ore contains enough of the metal for its extraction to be cost effective. We are beginning to rely on lower-grade ores.

Phytomining: Plants are grown on land containing the desired metal, the plants absorb the metal compound and concentrate it into their tissue. The plants are then harvested and burned with their ash containing a relatively high conc of the compound.

Bioleaching: Bacteria are mixed with the low-grade ore, the bacteria carry out reactions to produce a leachate (containing the metal compound we need). Scrap iron can then be used to displace the copper or electrolysis to separate it.

L6 - Life Cycle Assessment

We cannot be certain of exactly how damaging products are to the environment so we may have to make estimates or value judgements. Life-cycle assessments can also be biased.