chemistry earth and atmosphere

• Measuring the percentage of oxygen in the air method

  1. Heat the tube containing copper using a Bunsen burner

  2. Push in the plunger of syringe A to force the air into B

  3. When A is empty, push in the plunger of syringe B to force the air back to A

  4. Repeat several times

  5. As the air is pushed to and fro, the oxygen in the air reacts with the hot copper, forming copper (II) oxide, a black solid
• Measuring the percentage of oxygen in the air method (continued)

  1. Stop heating the tube after about 3 minutes

  2. Allow the apparatus to cool

  3. Push all the gas into one syringe and measure its volume

  4. Repeat steps 1 and 2 until the volume of the gas remains steady

  5. Note the final volume
• The final volume is less than 100 cm³
• This means all the oxygen in the 100 cm³ air has been used up
• test for hydrogen


  Test: Test the gas with a lighted splint. Result: A squeaky pop is heard /The gas extinguishes the splint with a squeaky pop.
• test for oxygen 


  Test: Test the gas with a glowing splint. Result: The splint relights.
• test for carbon dioxide

  Test: Bubble the gas into limewater. Result: The limewater turns milky/cloudy.
• test for water (1)


  Test: Add water to anhydrous copper (Il) sulfate.

  Result: It goes from white to blue.
• test for water (2)


  test: Add water to anhydrous cobalt (I) chloride.

  Result: goes from blue to pink
• The Present Atmosphere

  • nitrogen, 78%
  • Oxygen, 2 1
  • carbon dioxide,
  • 0.04% argon and other noble gases,
  • about 1% water vapour
• The Early Atmosphere

  • little or no oxygen a large
  • amount of carbon dioxide
  • water vapour
  • small amounts of other gases (methane, ammonia, nitrogen)
• There was a lot of volcanic activity on the early Earth and the gases produced by volcanoes formed the Earth's early atmosphere
• Volcanoes released large amounts of carbon dioxide and water vapour and small amounts of other gases, including nitrogen. These gases formed the Earth's early atmosphere. There was little or no oxygen in the Earth's early atmosphere (like the atmosphere of Mars and Venus). (Mars and Venus are rocky planets like the Earth).
• About 4 billion years ago, the amount of water vapour in the atmosphere decreased because the Earth cooled. Water vapour in the atmosphere condensed to liquid water forming the oceans. This is where primitive life first started.
• Small quantities of oxygen were first produced on the Earth about 3.5 billion years ago by primitive photosynthetic organisms like cyanobacteria that lived in shallow waters. Oxygen was released by cyanobacteria during photosynthesis.
• Small quantities of oxygen were first produced on the Earth about 3.5 billion years ago by primitive photosynthetic organisms like cyanobacteria that lived in shallow waters. Oxygen was released by cyanobacteria during photosynthesis.
• Cyanobacteria evolved into other forms of life, including green algae and primitive plants. Green algae and primitive plants released oxygen during photosynthesis, so the amount of oxygen in the atmosphere increased.
• During photosynthesis, carbon dioxide and water react to produce glucose and oxygen.
• Eventually the level of oxygen in the atmosphere increased enough to allow animals to evolve. Today, oxygen makes up about 21% of the Earth's atmosphere.
• The amount of carbon dioxide in the atmosphere decreased because was used by green algae and primitive plants for photosynthesis and some CO, dissolved in the oceans.
• How do scientists know that the earth's early atmosphere had little or no oxygen and was similar to the atmosphere of Mars and Venus?


  The earliest known rocks are about 4.1 billion years old and contain the mineral, iron pyrite, that would form if there was no oxygen around. There were no photosynthetie organisms on the early Earth, so the Earth's early atmosphere would be unchanged volcanic gases like the atmosphere of Mars and Venus.
• What evidence did the scientists have to prove that small amounts of oxygen were first produced on the Earth about 3.5 billion years ago?


  Stromatolites are over 3 billion years old, so support the idea that photosynthesis was occuring at that time. Stromatolites are formed by cyanobacteria which are organisms that photosynthesise. These bacteria grew in huge colonies and produce a sticky mucus that traps layers of sand and sediment. The layers build up to form rocky shapes called stromatolites.
• Reasons why carbon dioxide in the early atmosphere decreased

  1. Green algae and primitive plants used carbon dioxide for photosynthesis

  2. Some carbon dioxide dissolved in the oceans, so there was less in the atmosphere

  3. Sea creatures use dissolved carbon dioxide to make their shells, so the concentration of CO2 in the water goes down. This allows more CO2 from the atmosphere to dissolve in the oceans

  4. When the sea creatures died, their remains formed sedimentary rocks

  5. Some carbon dioxide reacts with water forming insoluble carbonates like calcium carbonate in shells and coral

  6. Some carbon dioxide became locked up in fossil fuels such as coal
• Reason why oxygen in the atmosphere increased


  Oxygen was released by photosynthetic organisms, green algae and primitive plants during photosynthesis.
• Reason why nitrogen in the atmosphere increased

  • There was an increase in nitrogen due to nitrogen accumulating because it is an unreactive gas that is released by volcanoes.
  • Ammonia reacted with the oxygen formed during photosynthesis.
• Evidence which proves that oxvgen in the atmosphere steadily inereased

  • The earliest known rocks that were about 4.l billion years old contained iron compounds that would form if there was no oxygen present.
  • Rocks dating from about 2.4 billion years ago contained a type of iron oxide, Fe3O4, which forms if there is only a little oxygen available.
  • Rocks dating from about 1.8 billion years ago contained a type of iron oxide, Fe203, which forms when there is much more oxygen present.
• The gases in the atmosphere that absorb energy are called greenhouse gases and include carbon dioxide, methane, CHI, and water vapour, H0. Without the greenhouse gases, the Earth would be too cold, about -18°C. If the Earth's atmosphere was too cold, water would not remain a liquid and there would be no life on this planet.
• the greenhouse effect

  • Energy from the Sun is transferred to the Earth in the form of high energy radiation.
  • Some of this energy is absorbed by the Earth's surface, warming it up.
  • The warm Earth emits (gives out) energy as infrared radiation,
  • The greenhouse gases (CO2, methane) absorb some energy radiated from the Earth.
  • When the gases re-emit the energy, some of it is transferred back to the Earth's surface warming it up.
• There has been a steady increase in the burning of fossil fuels for industry. During this period, carbon dioxide levels have increased. Increased levels of carbon dioxide and other greenhouse gases cause global warming. The increase in temperature of the Earth's surface will change weather patterns. This is called climate change
• As CO2 levels have risen, so has the average temperature of the Earth's surface. There is a strong corelation between CO levels and surface temperature.
• The evidence given below supports the idea that causes a rise in temperature because it shows how it could occur.

  1. Experiments done in the lab show that carbon dioxide can absorb infrared waves and their energy.
  2. Information from satellites shows that as levels in the atmosphere have increased, the amount of infrared waves leaving the Earth's atmosphere has decreased.
• global warming


  a gradual increase in temperature of the Earth's atmosphere.
• climate change


  alterations to global weather patterns.
• greenhouse effect


  atmospheric gases trapping energy.
• Today, the amount of carbon dioxide in the air is measured at monitoring stations around the world
• Evidence for historical carbon dioxide levels comes from measuring concentrations of the gas trapped in ice cores
• There are continuous temperature records for central England since 1659 but they cannot be used to assess global temperature changes because they are only from one place
• Earlier temperature measurements were not very accurate
• Modern thermometers


  Have a greater resolution and record the temperature continuously, so are less affected by a sudden anomalous change
• Today, we can also analyse temperature measurements from many different sources such as satellites and sensors