1. Do Now – 4 marks

2. Mark scheme

3. Boiling and evaporation
Learning today
What is evaporation
How to increase the rate of evaporation.
Condensation
Boiling

4. Solids, liquids and gases

5. Internal Energy
This is the sum of the kinetic energies - from motion of the particles and potential energies due to forces between the molecules in a substance
If you imagine the forces between particles as a spring, you can see if the particles are pulled apart or squashed together that energy is stored in the spring. Similarly there is potential energy between the particles in a substance.

6. Temperature
Temperature is a measure of the average random kinetic energy of the particles in a substance.
Note that they are not all travelling at the same speed.

7. Melting?
Changes in kinetic energy and potential energy?

8. Evaporation?
Changes in kinetic energy and potential energy?

9. Condensing?
Changes in kinetic energy and potential energy?

10. Freezing? Changes in kinetic energy and potential energy?
What is happening

11. Boiling and evaporation

12. Evaporation
Consider a beaker of water at room temperature

13. Evaporation
The molecules of water are moving around at different speeds, some fast, some slow.
# of molecules at a particular speed
speed of molecule (m/s)
Average speed

14. Evaporation
If a molecule is at the surface, and moving fast enough, it may escape the liquid. This is called evaporation.
Freedom!

15. Evaporation
Since the average speed of the remaining molecules must now be lower, the temperature of the liquid drops (since temperature is a measure of the kinetic energy of the molecules).
Freedom!

16. Evaporation – Please copy
If a molecule is at the surface, and moving fast enough, it has enough energy to break bonds and escape the liquid. This is called evaporation. It can happen at any temperature and as it is the molecules with the greater KE escaping the temperature of the liquid reduces.
Freedom!

17. Evaporation
If a molecule is at the surface, and moving fast enough, it has enough energy to break bonds and escape the liquid. This is called evaporation. It can happen at any temperature and as it is the molecules with the greater KE escaping the temperature of the liquid reduces.
Freedom!

18. Evaporation
If a molecule is at the surface, and moving fast enough, it has enough energy to break bonds and escape the liquid. This is called evaporation. It can happen at any temperature and as it is the molecules with the greater KE escaping the temperature of the liquid reduces.
Freedom!

19. Evaporation
Evaporation can thus take place at any temperature.

20. Increasing the rate of evaporation
Increasing the temperature.

21. Increasing the rate of evaporation
Increasing the temperature means that more molecules are moving fast enough to escape.

22. Increasing the rate of evaporation
Increasing the surface area

23. Increasing the rate of evaporation
Increasing the surface area means that more molecules are at the surface.

24. Increasing the rate of evaporation
Increasing the air flow over the surface

25. Increasing the rate of evaporation
Increasing the air flow over the surface so that molecules are carried away before they can fall back into the liquid

26. Increasing the rate of evaporation
Decreasing the humidity of the surrounding atmosphere

27. Increasing the rate of evaporation
Decreasing the humidity of the surrounding atmosphere to stop water molecules from the atmosphere entering the liquid.

28. please copy Evaporation can be increased by
Increasing temperature
more particles have a higher KE
Increasing the surface area
more particles closer to the surface
Increasing air flow above the surface
gives the particles somewhere to go to
- Evaporation and Condensation.flv

29. Boiling and evaporation

30. Boiling
Boiling occurs when vapour is produced in the body of the liquid.

31. Boiling
Boiling occurs when vapour is produced in the body of the liquid.
The bubble contains only water vapour, not air!

32. Boiling – Please copy
Boiling occurs when vapour is produced in the body of the liquid. This only happens at the boiling point of the liquid.
The bubble contains only water vapour, not air!

33. To summarize:
Evaporation takes place only at the surface of the liquid and can take place at any temperature.

34. To summarize:
Boiling means bubbles!
Boiling occurs when vapour is produced in the body of the liquid. This only happens at the boiling point of the liquid.

35. Evaporation -3 marks

36. Markscheme

37. Homework Homework – 1. Finish Draw these sentences
2. Stick in all your loose worksheets by Sunday 12th February
3 Java Lava Power

38. Homework If I give you homework you will do it
I will give you a blue slip if you do not

39. Got it?