Chemistry ✿ Chemistry of the atmosphere

how long ago was the Earth formed?

4.6 billion years

state the proportions of gases in the atmosphere today [3]

• nitrogen 78%

• oxygen 21%

• small amounts of carbon dioxide, water vapour and noble gases

how has oxygen increased during the early atmosphere?

algae and green plants produce oxygen during photosynthesis

what 2 processes have decreased carbon dioxide during the early atmosphere?

• algae and green plants take in carbon dioxide during photosynthesis

• formation of fossil fuels and sedimentary rocks use up carbon

name 3 greenhouse gases

carbon dioxide, methane, water vapour

Describe how carbon dioxide helps to maintain temperatures on Earth. [3]

• carbon dioxide allows short wavelength radiation to pass through the atmosphere

• to the earth’s surface

• carbon dioxide absorbs outgoing long wavelength radiation

explain the earth’s human greenhouse effect

• deforestation → cutting down of trees leads to less carbon dioxide being absorbed

• burning fossil fuels/ hydrocarbons → releases carbon dioxide

evaluate the evidence of climate increasing due to human activity

• evidence is peer-reviewed so that it is reliable

• However, it is hard to fully understand the earth’s climate as it is too complex, so models are simplified and inaccurate

state 4 risks of climate change

• polar ice caps melt, causing sea levels to rise leading to flooding

• rainfall patterns and temperatures change, affecting agriculture

• frequency of storms increase

• changes in temperature effects water availability

carbon footprint

the total amount of carbon dioxide released over the full life cycle of a product, service or event.

state 4 ways to reduce carbon footprints

• use renewable or nuclear energy sources

• using efficient processes can conserve energy and reduce waste, reducing methane emissions

• governments can tax companies based on amounts of emissions they produce

• trapping carbon dioxide before its released into atmosphere and store it deep underground

the __________ of fuels is a major source of atmospheric pollutants

combustion

equation for complete combustion

methane + oxygen → carbon dioxide + water

equation for incomplete combustion

methane + oxygen → carbon monoxide + water

carbon monoxide

a odourless, colourless, poisonous gas, so it is not easily detected

Explain the environmental effects of releasing carbon and sulphur into the atmosphere [6]

carbon dioxide is produced

• which increases global warming

• leading to polar ice caps to melt and rising sea levels

sulphur dioxide is produced

• which causes acid rain

• leading to buildings being eroded

Explain why soot (carbon particulates) is formed when some fossil fuels are burned [2]

• incomplete combustion

• due to insufficient oxygen

Fossil fuels are burned in car engines.

Explain how reducing the amount of sulfur in fossil fuels reduces the erosion of limestone. [4]

• sulfur reacts with oxygen to form sulfur dioxide

• so if less sulfur dioxide is emitted

• there will be less acidic rain

• so less limestone reacts with acid rain

Oxides of nitrogen are atmospheric pollutants which are formed in car engines.

Explain why oxides of nitrogen are formed in car engines. [2]

• car engines work at high temperatures

• so nitrogen from the engine reacts with oxygen from the air

When diesel burns in car engines, oxides of nitrogen are produced.

Where does the nitrogen come from? [1]

• from the air

Sulfur is a common impurity in diesel.

Explain why this causes an environmental problem [3]

• sulfur reacts with oxygen to form sulfur dioxide

• sulfur dioxide dissolves in rainwater, forming acid rain

• acid rain contaminates seas, killing wildlife

Describe how coal was formed from the carbon dioxide present in the Earth’s early atmosphere.

• carbon dioxide is absorbed during photosynthesis

• by plants

• which die and are compressed by sediment

• over millions of years

explain how greenhouse gases cause global warming [4]

• shortwave length radiation enters atmosphere as UV

• it is absorbed and reemitted as longer length radiation as inferred radiation

• radiation is absorbed by atmosphere

• this increases the temperature