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Air

Air . Chapter 31 Page 186. The Earth ’ s early atmosphere. Early atmosphere formed by gases given out by volcanoes. Mostly carbon dioxide with little or NO oxygen. Most of the water vapour condensed and formed oceans. Smaller proportions of water vapour, ammonia and methane.

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Air

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  1. Air Chapter 31 Page 186

  2. The Earth’s early atmosphere Early atmosphere formed by gases given out by volcanoes Mostly carbon dioxide with little or NO oxygen Most of the water vapour condensed and formed oceans Smaller proportions of water vapour, ammonia and methane Very similar to the atmospheres of Mars and Venus

  3. Changes to the early atmosphere

  4. What is air made of? Air is a mixture of different gasses • Nitrogen N2 • Oxygen O2 • Noble Gasses Ar • Carbon Dioxide CO2 • Water Vapour H2O

  5. Changes to today’s atmosphere Where has this increase in carbon dioxide come from? Burning fossil fuels!

  6. How can we prove air is a mixture? • Its composition varies – in compounds the composition is constant • If air is cooled down to low temperatures the gasses all become liquids at different temperatures – in compounds gasses would change state at the same time The components of air can be separated individually

  7. How can we prove air is a mixture? • When the gasses air mixed together in the right amounts they form air, no heat is given out or taken in so no new compound is made

  8. How can we show the amount of oxygen in air? The candle uses up all of the oxygen in the air until it goes out. The level that the water rises could be used to calculate approx. that 21% of air is made up of oxygen.

  9. How can we show that the air contains carbon dioxide? Carbon Dioxide, turns lime water milky.

  10. How can we show that the air contains water vapour? Turns blue cobalt chloride paper pink

  11. Oxygen Oxygen is prepared in the lab by looking at the breakdown of Hydrogen Peroxide This is however a very slow reaction so we use a substance called a catalyst A Catalyst is a substance that speeds up a chemical reaction without being used up in the reaction

  12. Oxygen Chemical equation: 2H2O2 2H2O + O2 Hydrogen Peroxide Water + Oxygen MnO2 Manganese Dioxide

  13. Oxygen Properties: • Oxygen is a colourless, odourless, tasteless gas • Oxygen is slightly heavier than air • Oxygen is slightly soluble in water • Oxygen is a neutral gas, it is not acidic or basic 5. Oxygen relights a glowing splint – this is the test for oxygen 6. Oxygen is a very reactive element. It combines with other elements to form oxides

  14. Oxygen Acidic – Carbon dioxide C + O2 CO2 Basic – Magnesium Oxide 2Mg + O2 2MgO

  15. Oxygen Uses: • Breathing – our cells need oxygen to release energy from our food • Welding – Cutting and welding requires a very hot flame, this is achieved when acetylene is mixed with oxygen • Burning – Oxygen is needed for the burning of fossil fuels

  16. Preparing oxygen We will look at this next week

  17. 03/12/13

  18. Preparing Oxygen Today we will • Prepare oxygen using hydrogen peroxide and manganese dioxide • Conduct the tests for oxygen

  19. Preperation of Oxygen

  20. Remember: Reactants  Products Oxygen Chemical equation: 2H2O2 2H2O + O2 Word Equation : Hydrogen Peroxide Water + Oxygen MnO2 Manganese Dioxide

  21. Testing for Oxygen • Relight a glowing splint • Neutral – moist red and blue litmus stay red and blue

  22. 10/12/13

  23. Today we will… Look at the production of Carbon dioxide • How it is produced • Its properties • Its Uses • We will make some!

  24. Carbon Dioxide Carbon Dioxide can be prepared in the lab by reacting dilute, Hydrochloric acid and marble chips Calcium carbonate + Hydrochloric acid  Calcium Chloride + Water + Carbon Dioxide CaCO3 + 2HCl  CaCl2 + H2O + CO2

  25. Properties of Carbon Dioxide • CO2is a colourless, odourless, tasteless gas • It is an acidic gas – Turns blue litmus paper red • Does not support combustion (burning) • It is denser than air

  26. Properties of Carbon Dioxide 5. It turns limewater milky – this is the test for carbon dioxide Ca(OH)2 + CO2  CaCO3 + H2O Limewater + Carbon dioxide  Chalk + Water

  27. Properties of Carbon Dioxide 6. It dissolves in water to form an acidic solution that turns blue litmus paper red CO2 + H2O  H2CO3 Carbon dioxide + Water  Carbonic Acid

  28. Uses of Carbon Dioxide • Photosynthesis – green plants use it to make their food • Fire Extinguishers – puts out fires • Fizzy Drinks – It is dissolved under high pressure in fizzy drinks

  29. The Production of CO2 (Pg 105)

  30. Procedure • Set up as shown (calcium carbonate is the chemical name for marble chips). • Slowly release the hydrochloric acid into the flask underneath. • Carbon dioxide is collected it the gas jar • Test 1: Pour a small volume of limewater into the jar and shake – the limewater will turn milky showing that the gas is carbon dioxide. • Test 2: Add water to a fresh jar of carbon dioxide and test with blue litmus paper: it turns red demonstrating that it is an acid.

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