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

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

7. 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. Temp (°C) Time (mins) Melting point

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

9. Cooling curve Why does this happen?

10. 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. Energy released (“latent” = “hidden”)

11. 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) Temp (°C) Time (mins) Melting point solid liquid Energy absorbed

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

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

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

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