Chemistry

• What is the % of nitrogen in our current atmosphere?

  78
• What is the % of oxygen in our current atmosphere?

  21
• What is the % of carbon dioxide in our current atmosphere?

  0.04
• What is the % of argon in our current atmosphere?

  0.9
• Describe how the early atmosphere was formed?


  Frequent volcanic eruptions released gases
• Name the main gases in the early atmosphere?

  Carbon dioxide, methane, ammonia and water vapour
• Explain how the levels of oxygen increased.


  The evolution of plants caused carbon dioxide to be absorbed and changed into oxygen by photosynthesis, which is released
• Explain how the levels of carbon dioxide decreased.

  Carbon dioxide is absorbed by plants for use in photosynthesis. It is dissolves into the oceans and becomes locked up into sedimentary rocks/fossil fuels
• Explain how nitrogen levels increased.

  Ammonia + Oxygen → Nitrogen + Water
• Explain why nitrogen levels have remained constant in the atmosphere.

  Nitrogen isn't a very reactive gas
• Name 3 greenhouse gases.

  Carbon dioxide, methane and water vapour.
• Describe how the greenhouse effect is caused.


  1.Electromagnetic radiation from the Sun passes through the Earth's atmosphere.

  2.The Earth absorbs electromagnetic radiation with short wavelengths and so warms up. Heat is radiated from the Earth as longer wavelength infrared radiation.

  3.Some of this infrared radiation is absorbed by greenhouse gases in the atmosphere.

  4.The atmosphere warms up.
• Define term global warming.

  Gradual increase in the average temperature of the Earth
• Define term carbon footprint.


  The total amount of carbon dioxide produced to directly and indirectly by human activities (in tonnes of CO₂
• Define term climate change.

  Large-scale, long-term shift in the Earth's weather patterns or average temperatures.
• Explain how human activity causes global warming.

  Increased levels of carbon dioxide in the atmosphere cause more heat radiation to be trapped and cause the average temperature of the Earth to increase.
• Name 3 effects of climate change.

  Polar ice melts, sea levels rise and low lying land floods.
• Name 3 steps to reduce your carbon footprint.

  Use of alternative fuels (e.g. hydrogen), reduce/reuse/recycle and use public transport/walk
• How is carbon dioxide formed?

  Complete combustion of fuels
• How is carbon monoxide formed?

  Incomplete combustion of fuels
• How is carbon particulates are formed?

  Incomplete combustion of fuels
• How is sulphur dioxide formed?

  Sulphur impurities in fuels react with oxygen during combustion
• How are nitrogen oxides formed?


  Nitrogen and oxygen from the air react in the hot engine
• Name the environmental effect caused by carbon dioxide.

  Global warming
• Name the environmental effect caused by carbon monoxide.

  Breathing difficulties
• Name the environmental effect caused by carbon particulates.

  Global dimming and cancer
• Name the environmental effect caused by sulphur dioxide.

  Acid rain (kills fish/plants and erodes limestone)
• Name the environmental effect caused by nitrogen oxides.

  Acid rain (kills fish/plants and erodes limestone)
• Phase 1 - volcanoes released gases

  - surface was covered in volcanoes that erupted and released lots of gases which formed the early atmosphere, which consisted of mostly carbon dioxide with virtually no oxygen.

  - volcanic activity also released nitrogen which built up in the atmosphere over time, as well as water vapour and small amounts of methane and ammonia
• What is Earth's early atmosphere most similar to?

  The atmospheres of Mars and Venus today
• Phase 2 - oceans, algae and green plants absorbed carbon dioxide

  1) As the earth cooled, water vapour condensed and fell as rain, collecting in hollows in the Earth's crust and forming the first oceans.

  2)When the oceans formed carbon dioxide dissolved in the water and the carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere.

  3) Green plants and Algae evolved and absorbed some of the carbon dioxide for photosynthesis. Later marine animals evolved. Their shells and skeletons contained carbonates from the oceans.

  (when animals eat plants, some of the carbon is transferred into animal tissues)

  4) Some of the carbon these organisms took in from the atmosphere and oceans became locked up in rocks and fossil fuels after they died.
• How did the formation of fossil fuels reduce CO2 levels in the atmosphere?

  - plants, plankton and marine animals fall to the seabed after they die and are buried by layers of sediment and compressed

  - they remain subject to high heat and pressure over millions of years

  - form sedimentary rocks, oil and gas - trapping the carbon within them and helping to keep CO2 levels in the atmosphere reduced
• How is crude oil and natural gas formed?

  - the remains of plankton were deposited in muds on the sea floor and were covered over and compressed over millions of years

  - producing crude oil and natural gas that became trapped in the rocks
• How is coal (sedimentary rock) formed?

  - formed from thick plant deposits

  - these dead plants were buried, so no oxygen was present

  - over millions of years they were compressed to form coal
• How is limestone formed?

  it is a sedimentary rock made mostly of calcium carbonate deposits, formed from the shells and skeletons of marine organisms
• Give two ways in which carbon dioxide was used up before life evolved on Earth:

  - Dissolved in oceans

  -Reacted with metal oxides forming carbonate compounds which fell as sediments
• Phase 3 - green plants and algae produced oxygen

  1) About 2.7 billion years ago, algae (and then green plants) use light to convert carbon dioxide into sugars and oxygen is released in photosynthesis .

  2) Animals carry out respiration where glucose and oxygen are converted into carbon dioxide and energy, which is released into the atmosphere.
• 200 million years ago, the atmosphere reached a composition similar to what it is today:

  80% nitrogen

  20% oxygen

  small proportions of various other gases including carbon dioxide, water vapour and noble gases
• How are scientists able to reconstruct the early atmosphere?

  - evidence from gas bubbles trapped in ancient rocks

  - data gathered from atmospheres of other planets
• How does ammonia and methane from react with oxygen?

  2CH4 + 3O2 -> 2CO2 + 4H2O

  4NH3 + 3O2 -> 2N2 + 6H2O