Chemistry of the Atmosphere Flashcards
what is the percentage composition of the atmosphere?
- 78% nitrogen
- 21% oxygen
- 1% all other gases incl. water vapour and CO2 (0.03%)
what was the atmosphere like 4.6 billion years ago?
- massive amounts of volcanic activity helped the earth cool down more quickly by releasing heat energy
- large amounts of CO2 released, as a consequence, along with water vapour - but the earth’s surface was still too hot for the water vapour to condense onto - at this time the atmosphere was ~90% CO2
what was the atmosphere like 3.4 billion years ago?
- the earth’s surface became cool enough for water to condense onto it, allowing lakes, rivers and oceans to develop
- CO2 dissolved into the developing oceans, enabling the amount of CO2 in the atmosphere to decrease
what was the atmosphere like 2.7 billion years ago?
- plants and algae photosynthesised, decreasing CO2 and increasing O2 levels
- O2 reacted in the atmosphere to produce ozone (O3) providing a protective layer of gas around the outer limits of the atmosphere, protecting life on earth from UV radiation
what was the atmosphere like 200 million years ago?
- oxygen rich, CO2 poor
- Nitrogen levels in the atmosphere begin to increase as denitrifying bacteria in soil break down compounds containing nitrogen
describe 5 ways in which today’s atmosphere is different from that of the Earth 4.6 billion years ago
- Higher oxygen levels
- higher nitrogen levels
- lower co2 levels
- less water vapour
- less hydrogen
describe the 4 key events that scientists theorise have changed the composition of the Earth’s atmosphere, from what is was 4.6 billion years ago to what it is today
- earth’s surface cooled enough for water vapour to condense on it
- CO2 dissolved in newly formed oceans and rivers
- plants and algae that photosynthesise began to evolve, increasing O2 and decreasing CO2 levels
- denitrifying bacteria began to break down nitrogen-containing compounds
what were the factors that reduced atmospheric carbon dioxide levels?
- formation of the oceans
- photosynthetic organisms evolved
- evolution of marine animals
how is human activity causing CO2 levels to rise?
- by unlocking carbon dioxide that has been locked up in fossil fuels and sedimentary rocks
- deforestation
- cattle farming
how is carbon dioxide unlocked from fossil fuels and sedimentary rocks?
- burning fossil fuels releases locked-up CO2 and energy - CH4 + O2 ⇒ CO2 +H2O
- thermal decomposition of limestone to produce cement and concrete released locked-up CO2 - CaCO3 ⇒ CaO + CO2
how do greenhouse gases cause global warming?
- UV radiation with a short wavelength comes from the sun and hits the earth’s surface
- it reflects as longer wavelength infra-red radiation but can’t get through the greenhouse gases, so the heat gets trapped
how do greenhouse gases help to support life on earth?
stop infra-red radiation passing out of the atmosphere and trapping heat which maintains a suitable temperature for life to thrive.
give two potential consequences of rising sea levels
Increased flooding and loss of coastal habitats/coastal erosion
give some potential consequences of climate change
Rising sea levels, extreme weather events, loss of biodiversity, crop failure and famine, drought
name 5 atmospheric pollutants from burning fossil fuels
- Carbon monoxide
- sulfur dioxide
- nitrogen oxides (NOx gases)
- carbon particulates
- carbon dioxide
what are NOx gases caused by?
oxygen and nitrogen in the atmosphere reacting in very hot engines
why are NOx gases bad?
they cause acid rain
what is a remedy for NOx gases in the atmosphere?
use a catalytic converter to convert NOx gases back into nitrogen and oxygen
what is sulfur dioxide in the atmosphere caused by?
Burning of fossil fuels containing sulfur, which reacts with oxygen
why is sulfur dioxide in the atmosphere bad?
it causes acid rain
what is a remedy for sulfur dioxide in the atmosphere?
remove sulfur from fuel and use FGD (flue-gas desulfurization)
what are carbon particulates in the atmosphere caused by?
Incomplete combustion of fuels, creating smoke
why are carbon particulates in the atmosphere bad?
create smog and poor air quality in turn, causing respiratory problems
what is a remedy for carbon particulates in the atmosphere?
Using filters in industrial processes to capture carbon particulates or do complete combustion by providing more oxygen
