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2. Bulgaria

6. Physics lesson 9 class

8. EVAPORATION AND BOILING Compare the processes on these points:  Start and final state of the matters  Conditions necessary for the process  Temperature changes  Internal energy

9. SPIRITS EVAPORATION  Watch the changing of the temperature during spirits evaporation  Make an inference

10. BOILING OF WATER  How does the temperature change during the heating of the water?  Watch the changes in the liquid

11. 1. EVAPORATION  EVAPORATION-the process of molecule separation from the free liquid surface  Liquid is changing into vapour  During evaporation the fastest molecules leave the free surface and the molecules,that remain in the liquid,have smaller kinetic energy. This is way the liquid cools down.

12. 2. BOILING  Boiling-the process vaporization from the whole volume of the liquid  At constant pressure, while the liquid is boiling, despite the heat supply, the temperature remains constant /boiling point/  The boiling point is a quantity characteristic of the deferent liquids  The boiling point of a liquid depends on external pressure- when the pressure is higher, the boiling point rises  Latent heat of vaporization/r/-the quantity of heat, needed for a unit mass of a given liquid to be turned into vapor at constant temperature  r=Q/m

13. 3. CONDENSATION  Condensation-process of changing vapour into liquid

14. ON-LINE PHYSICS LAB INDIVIDUAL ACTIVITIES INDIVIDUAL ACTIVITIES IN INTERACTIVE EXPERIMENTS  Fit together the necessary equipment and examine the process under following conditions: –Constant temperature –Heating –Cooling

15. 4. PUTTING EVAPORATION AND BOILING INTO PRACTICE  Distillation  Separating composites  Autoclaves  Vacuum apparatuses

16. EXAMINE YOURSELF  1. You have to watch evaporation at: А) Low temperature B) High temperature C) Any temperature

17. Mistake! NextPrevious question

18. Correct! NextPrevious question

19. Mistake! NextPrevious question

20. Correct! NextPrevious question

21. Mistake!

22. Correct! Previous question

23. Examine yourself  2.What is the correlation between waters boiling point in open container at see level /T 1 / and on the mountain top/T 2 /? А) Т 1 = Т 2 B) Т 1 > Т 2 C) Т 1 < Т 2

24. Examine yourself  3. What amount of heat is required for the complete evaporation of 200 g water at temp.100 °C? ( r = 2260 kJ/kg) А) 4,52.10 5 J B)2,26.10 5 J C) 4,52.10 7 J

25. THANK YOU FOR YOUR ATTENTION!