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Do now!

Can you also look through the comments in your book?. Do now!. Can you finish the “fractional distillation” sheet you started on Friday?. Air?. Air. 78% Nitrogen 21% Oxygen 0.93% Argon and other noble gases 0.04% carbon dioxide Variable amounts of water vapour

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Do now!

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  1. Can you also look through the comments in your book? Do now! Can you finish the “fractional distillation” sheet you started on Friday?

  2. Air?

  3. Air • 78% Nitrogen • 21% Oxygen • 0.93% Argon and other noble gases • 0.04% carbon dioxide • Variable amounts of water vapour • Variable amounts of pollutant gases

  4. Oxygen • Extracted from air by fractional distillation • If air is cooled down, at -183°C oxygen condenses into a liquid (at -196°C Nitrogen condenses too)

  5. Cooling

  6. Melting point Temp (°C) Time (mins) Cooling curve In the experiment, you will have noticed that the temperature of the wax stopped changing as the waxchanged from a liquid to a solid.

  7. Melting point Temp (°C) Time (mins) Cooling curve This always happens during a change of state

  8. Cooling curve Why does this happen?

  9. Energy released (“latent” = “hidden”) Latent heat When the molecules of a substance settle into the regular pattern of a solid, energy is released as bonds are formed. This energy released is called latent heat. This stops the temperature from falling.

  10. Energy absorbed Latent heat The opposite happens when a solid melts. Heat is needed to break the bonds between the solid particles (instead of raising the temperature) liquid Melting point Temp (°C) solid Time (mins)

  11. 0°C 0°C Melting ice Heat energy is needed for converting iceat 0ºC to water at 0ºC This heat energy is needed to melt the ice, NOT make it hotter

  12. 0°C 0°C Freezing water Heat energy is released when water at 0ºC is converted to ice at 0ºC This heat is keeps the temperature constant whilst the water is freezing.

  13. Evaporating water Heat energy is absorbed by the water when changing to a gas, keeping the temperature constant. 100°C 100°C

  14. Got it? Can you stick the summary sheet into your book?

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