the atmosphere

• The atmosphere is the layer of gases that surrounds the earth. The abundance (amount) of each gas in the atmosphere has changed over time, but at the moment it is almost all nitrogen and oxygen:

  78% nitrogen (N2)

  21% oxygen (O2)

  Almost 1% Argon (Ar)

  0.04% carbon dioxide (CO2)
• When you burn (combust) something in air, it reacts with the oxygen in the atmosphere to form an oxide. These oxides can be acidic, neutral, or alkaline.
• Magnesium.

  • Burns with a bright white flame.
  • Forms a white powder of magnesium oxide.
  • Magnesium oxide is alkaline when it's dissolved in water.
  • 2Mg(s) + O2(g) ➔ 2MgO(s)
• Hydrogen.

  • Burns easily, produces a pale blue flame
  • Burning hydrogen forms water vapour (which has a neutral pH)
  • 2H2(g) + O2(g) ➔ 2H2O(g)
• Sulfur.

  • Burns with a pale blue flame.
  • Produces sulfur dioxide.
  • Sulfur dioxide is acidic when dissolved in water.
  • S(s) + O2(g) ➔ SO2(g)
• When you heat a metal carbonate it will break apart into a metal oxide and carbon dioxide:

  Metal carbonate  ➔  metal oxide + carbon dioxide
• how are global warming and climate change different?

  Global warming refers to the overall increase in the earths temperature whereas climate change is a consequence of global warming and refers to the effects on the climate, such as large scale shifts in weather patterns
• One effect of global warming is the melting of ice caps. This will increase the volume of water in the ocean and could lead to seasonal flooding, or the submersion of entire islands. This is made worse by the fact that water expands when it is heated, so it will also increase in volume.
• Describe how copper can be used to show the percentage of oxygen in the air

  Copper is put in a large tube between two gas syringes

  One gas string contains 100cm cubed of air

  One gas syringe is empty, pushed all the way in

  Copper is then heated strongly using a Bunsen burner

  Air is passed over the copper using a syringe

  The oxygen reacts with the air to form copper (II) oxide - CuO

  The air is then cooled and the volume of air in the syringe decreases to 80 cm cubed
• Describe the observations when magnesium burns in oxygen

  Intense white flame

  white powder produced

  white solid forms