Earth and Atmosphere Flashcards
What percentage of the atmosphere today is made up of
nitrogen?
78%
What percentage of the atmosphere today is made up of
oxygen?
21%
What percentage of the atmosphere today is made up of
argon?
0.9%
What percentage of the atmosphere today is made up of
carbon dioxide?
0.037%
How long ago did cyanobacteria evolve?
2.7 billion years ago
What was so special about
cyanobacteria?
they were the first creature to photosynthesise
What is the equation for
photosynthesis?
carbon dioxide + water -> oxygen + glucose
6CO2 + 6H2O -> 6O2 + C6H12O6
Where is most of the carbon from the original carbon dioxided now locked up in?
- coal
- natural gas
- sedimentary rock
- oil
What are the causes of
carbon dioxide
as a pollutant in the air?
combustion
respiration
What are the causes of
sulfur dioxide
as a pollutant in the air?
burning of coal
(burning the sulfur impurities)
What are the causes of
carbon particulates (soot)
as a pollutant in the air?
burning wood and fossil fuels
What are the causes of
carbon monoxide
as a pollutant in the air?
incomplete combustion
What are the causes of
nitrogen dioxide
as a pollutant in the air?
internal high temperature combustion engines
(e.g. cars)
What effects on the environment does the air pollutant carbon dioxide have?
it reflects radiation back into the earth’s atmosphere - contributing to global warming
(and the greenhouse effect)
What effects on the environment does the air pollutant sulfur dioxide have?
It binds with water vapour in clouds to produce acid rain. This acid rain destroys forests, erodes limestone buildings and kills aquatic life.
What effects on the environment does the air pollutant soot have?
it can cause lung damage and lung cancer
What effects on the environment does the air pollutant carbon monoxide have?
it binds to haemoglobin in the blood and stops oxygen from getting to cells
What effects on the environment does the air pollutant nitrogen dioxide have?
it forms photochemical smog
(and acid rain)
How is acid rain formed?
- Fuels contain sulfur compouds as impurities and when burnt will generate sulfur dioxide (SO2).
- This sulfur dioxide then reacts with water to make ‘sulfurous acid’, H2SO3.
- Sulfurous acid reacts with oxygen to form sulfuric acid, H2SO4.
- A combination of acids fall as acid rain.
What problems are caused by
acid rain?
- it destroys forests
- it erodes limestone buildings
- it kills aquatic life
What are the benefits of burning hydrogen as an alternative?
- it is more efficient
- it is a renewable resource
What is the difference between
green hydrogen and blue hydrogen?
Green Hydrogen:
- from electrolysing water using photovoltaic cells (from the sun)
Blue Hydrogen:
- from the reaction between methane (not renewable) and steam
- this uses non-renewable resources to create a greenhouse gas :[[[
What are the positives of
hydrogen in cars?
- lower engine temperature
- no pollutants formed during driving
What are the negatives of
hydrogen in cars?
- highly explosive
- not readily available
- difficult to store safely
- low density (low energy to volume ratio)
What makes water
safe to drink?
- low salt concentration
- free from pathogens
- no large particles
What steps are necessary to obtain
potable water?
- choose a source of water
- filter to remove large objects
- sterilise (kill microbes)
How can desalination be carried out?
- distillation
- reverse osmosis using membranes
this process requires a lot of energy
What are the steps that are necessary to treat waste water?
- Screening and grit removal
- Sedimentation to produce sewage sludge and effluent
- Anaerobic digestion of sewage sludge
○ Biogas produced
○ Remaining sludge can be used as fuel - Aerobic biological treatment of effluent
○ Effluent can now be discharged back into rivers
What formed the Earth’s early atmosphere?
gases produced by volcanic activity
What was Earth’s early atmosphere thought to contain?
- little or no oxygen
- a large amount of carbon dioxide
- water vapour
- small amounts of other gases
How did Earth’s oceans form?
- The earth has just formed and is a ball of molten rock.
- Its atmosphere consists of hydrogen and helium.
- As the ball cools, a crust forms
- Volcanoes burst forth from the molten rock below.
- These volcanoes erupt and gave out gases such as carbon dioxide, ammonia, methane and steam.
- As the earth cools down even more, this steam condenses and falls as rain.
- It fills up hollows in the Earth’s crust and thus the oceans are formed.
How did organisms start life on land?
- At first, there is no ozone layer, so the UV light from the sun is too intense for anything to live on land. So the first living things appear in the oceans.
- These organisms evolve into simple plants, like algae.
- These organisms use up carbon dioxide in photosynthesis and make the first molecules of oxygen.
- After some time, the oxygen starts to build up in the atmosphere. Some of this reacts to form the ozone layer, which shields the Earth from harmful UV light.
- This allows organisms to leave the water and start to live on land.
What is the chemical test for oxygen?
- collect the gas in a test tube
- test with a glowing splint
- oxygen will relight a glowing splint
