Chemistry In The Atmosphere Flashcards
Describe the proportions of gases in the modern atmosphere
- Around 80% of N2
- 20% of O2,
- Small quantities of CO2, H2O, and noble gases
Describe the Earth’s early atmosphere and how it was formed
a) The Earth was hot when it was formed
b) There was significant volcanic activity
c) Gases have been released from these volcanoes
d) These gases included CO2, N2, CH4, NH3, H2O
How did the amount of oxygen in the atmosphere increase?
Algae and plants produced the atmospheric O2 by photosynthesis, which can be represented by the equation: 6 CO2+ 6 H2O → C6H12O6+ 6 O2. As the amount of gradually O2 increased, there were more plants that produced more oxygen.
How did the amount of carbon dioxide in the atmosphere decrease?
a) Some CO2 was dissolved in the oceans, where it reacted with metal ions to form
insoluble carbonates, such as CaCO3, or was taken in by animals to become a part of
skeleton. When animal dies, this becomes a sedimentary rock.
b) Some CO2 was used in photosynthesis to make oxygen.
What is the greenhouse effect? What are greenhouse gases? Give examples
Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life.
They allow short wavelength radiation from the sun to pass through the atmosphere to the Earth’s surface, but absorb the outgoing long wavelength radiation from the Earth causing an increase in temperature.
Water vapour, carbon dioxide, and methane
Why is the greenhouse effect necessary for life?
The greenhouse effect is a natural phenomenon. Without it, the Earth would be too cold for life to exist.
How have human activities led to an increase in greenhouse gases?
Carbon dioxide - combustion and deforestation
Methane - increased farming and decomposition in landfills
What are the potential effects of global climate change?
• sea level rise, which may cause flooding and increased coastal erosion
• more frequent and severe storms
• changes in the amount, timing and distribution of rainfall
• temperature and water stress for humans and wildlife
• changes in the food-producing capacity of some regions
• changes to the distribution of wildlife species
What is a carbon footprint?
The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
What actions can be taken to reduce a carbon footprint?
• increased use of alternative energy supplies
• energy conservation
• carbon capture and storage (where CO2 is trapped in solvents and stored
underground)
• carbon taxes and licences
• carbon off-setting including through tree planting
• carbon neutrality - zero net release.
What are the challenges faced with reducing a carbon footprint?
• scientific disagreement over causes and consequences of global climate change
• lack of public information and education
• lifestyle changes (people don’t want to give up their cars)
• economic considerations (it will cost money)
• incomplete international cooperation
What are the advantages of complete combustion?
• less soot (carbon particulates) is made with complete combustion
• more heat per gram of fuel is released with complete combustion
• poisonous carbon monoxide is not produced with complete combustion
How is pollution caused by combustion?
When a fuel burns, the gases released to the atmosphere include carbon dioxide, water (vapour), carbon monoxide, sulphur dioxide and oxides of nitrogen.
Solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere.
What are the issues regarding sulfur dioxide and oxides of nitrogen?
Sulfur dioxide and oxides of nitrogen cause respiratory problems in humans and cause acid rain. Acid rain damages plants and buildings.
What problems do particulates cause?
Particulates, such as carbon particles, cause global dimming by reducing the amount of sunlight that reaches the Earth’s surface. Particulates cause health problems for humans because of damage to the lungs.
What is sustainable development?
Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs
In the UK, potable water is produced by?
• choosing an appropriate source of fresh water
• passing the water through filter beds to remove any solids
• sterilising to kill microbes
What are the sterilising agents for potable water?
Sterilising agents used for potable water include chlorine, ozone or ultraviolet light.
• Chlorine is a toxic gas so the amount added to water has to be carefully monitored.
• Using ultraviolet light to kill microbes avoids adding chemicals to the water but is more expensive
How is desalination carried out?
Desalination can be done by distillation or by processes that use membranes such as reverse osmosis. These processes require large amounts of energy.
What is reverse osmosis?
Sea water is passed through a membrane that only allows through the water molecules. It needs high pressure to push the water through the membrane. The high pressure requires a lot of energy to produce.
How is wastewater produced and how is it treated?
Urban lifestyles and industrial processes produce large amounts of waste water that require treatment before being released into the environment. Sewage and agricultural waste water require removal of organic matter and harmful microbes. Industrial waste water may require removal of organic matter and harmful chemicals.
What are the processes involved in sewage treatment?
Sewage treatment includes:
• screening and grit removal
• sedimentation to produce sewage sludge and effluent
• anaerobic digestion of sewage sludge
• aerobic biological treatment of effluent.
What do new methods of mining avoid in terms of disadvantages of traditional mining?
Avoids the disadvantages of traditional mining methods of digging, moving and disposing of large amounts of rock
What is phytomining?
Phytomining uses plants to absorb metal compounds from the soil. The plants are harvested and then burned to produce ash that contains the metal compounds.
What is bioleaching?
Bioleaching uses bacteria to produce leachate solutions that contain metal compounds
What are the main advantages and disadvantages of phytomining and bioleaching?
These methods need less energy than traditional methods, and can work on low concentration ores but are slow to carry out.
Describe the stages of LCAs
Life Cycle Assessments (LCAs) are carried out to assess the environmental impact of products in each of these stages:
- extracting and processing raw materials
- manufacturing and packaging
- use and operation during its lifetime
- disposal at the end of its useful life, including transport and distribution at each stage.
How do we reduce the use of resources?
The reduction in use, reuse and recycling of materials by end users reduces the use of limited resources, energy consumption, waste and environmental impacts.
What are advantages and disadvantages of recycling?
Advantages of recycling: less acid rain (pollution) metal ore reserves last longer / conserved energy for extraction saved less mining / quarrying less waste less landfill creates local employment
Disadvantages of recycling ; collection problems transport problems/ cost of transport difficult to separate metal from appliances/sort
What is corrosion and how is it prevented?
Corrosion is the destruction of materials by chemical reactions with substances in the environment, e.g. rusting.
Corrosion can be prevented by applying a coating that acts as a barrier, such as greasing, painting or electroplating. These methods stop the air or water coming into contact with the metal.
Describe sacrificial protection
Some coatings are reactive and may contain corrosion inhibitors or a more reactive metal.
If two metals are in contact the more reactive metal will corrode instead of the less reactive one, e.g. zinc is used to galvanise iron and when scratched, provides sacrificial protection because zinc is more reactive than iron.
Describe the compounds and the uses of bronze, brass, gold, silver, copper, zinc, aluminium-magnesium and steels
Alloys:
Bronze - an alloy of copper and tin, used for making statues and decorative objects.
Brass - an alloy of copper and zinc used for producing water taps and door fittings.
Gold used as jewellery is usually an alloy with silver, copper and zinc (The proportion of gold in the alloy is measured in carats, with pure gold being 24 carat, e.g. 18 carat gold is 75% gold.)
Aluminium - magnesium alloys are low density and used in aerospace manufacturing.
Steels - alloys of iron that contain specific amounts of carbon and other metals. High carbon steel is strong but brittle. Low carbon steel is softer and more easily shaped. Steels containing chromium and nickel (stainless steels) are hard
How are properties of polymers determined?
The properties of polymers depend on what monomers they are made from and the conditions under which they are made. For example, low density (LD) and high density (HD) poly(ethene) are produced from ethene, using different catalysts and reaction conditions.
Describe the structures of thermosoftening and thermosetting polymers
Thermosetting polymers do not melt on heating. The polymer molecules are linked to each other by strong cross-links. Thermosoftening polymers soften easily on heating and can then be remoulded, keeping the new shape on cooling. The polymer molecules are attracted to each other by weak intermolecular forces.
How is glass made?
Most of the glass we use is soda-lime glass, made by heating a mixture of sand, sodium carbonate and limestone. Borosilicate glass, made from sand and boron trioxide, melts at higher temperatures than soda-lime glass
How are clay ceramics made?
Clay ceramics, including pottery and bricks, are made by shaping wet clay and then heating in a furnace.
How are composites formed?
Fibres or fragments of one material (reinforcement) are surrounded by a binder/matrix material that holds these fibres/fragments together.
E.g. fibreglass - glass fibres bound together in a polymer, used for making storage tanks.
Outline the key points of Haber process. Include the use of the product.
a) The purified H2 and N2 gases are passed over Fe catalyst at a high temperature (about 450 °C) and a high pressure (about 200 atm)
b) Fe speeds up the rate of reaction, so that a lower temperature could be used in the process.
c) Some of the hydrogen and nitrogen reacts to form ammonia. N2 + 3 H2 ⇌ 2 NH3
d) The reaction is reversible so ammonia breaks down again into nitrogen and hydrogen.
e) On cooling, the ammonia liquefies and is removed. The remaining hydrogen and nitrogen are recycled. This means almost no material is wasted.
f) Ammonia is used for production of nitrogen-containing fertilisers.
How are compounds of nitrogen, phosphorus and potassium used?
Compounds of nitrogen, phosphorus and potassium are used as fertilisers to improve agricultural productivity. NPK fertilisers contain compounds of all three elements
How is industrial production of NPK fertilisers achieved?
Ammonia can be used to manufacture ammonium salts. The ammonium sulfate, phosphate, and nitrate can be produced by reaction of ammonia with the requisite acid.
2 NH3 + H2SO4 → (NH4 )2SO4
2 NH3 + H3PO4 → (NH4 )3PO4
NH3 + HNO3 → NH4NO3
How is the phosphate rock utilised in the production of fertilisers?
• Phosphate rock is reacted with nitric acid to produce phosphoric acid and calcium nitrate.
• Phosphate rock can be reacted with sulfuric acid to produce a mixture of calcium phosphate and calcium sulfate
• Phosphate rock can be reacted with phosphoric acid to produce calcium phosphate.
The Haber process uses high T and p conditions. Explain why this is so and why this is a compromise.
The conditions are a compromise between rate and the yield:
• The reaction is exothermic. An optimum temperature of 450 °C is used. Using a lower temperature would give a higher yield, but the rate of NH3 production would be too slow.
• A pressure of 200 atm is used. Using a higher pressure would give a higher yield, but would be too expensive, because of the cost of energy to produce the high pressure.
How is water vapour decreased?
Water condensed as the earth cooled forming oceans
How is carbon dioxide decreased?
Dissolving in the oceans, forming sedimentary rocks and photosynthesis
What is the equation for photosynthesis?
Carbon dioxide + water -> glucose + oxygen
How is oxygen increased?
By photosynthesis of algae and bacteria
What are sedimentary rocks?
Rock that forms when sediments such as carbonates and dead organisms are squashed together over time
What is pollution?
Release of harmful materials into the environment
What is the cause of carbon dioxide pollution?
Combustion of fossil fuels
What is the effect of carbon dioxide pollution?
Global warming
