2. States Three states of matter : solid, liquid and gas Melting : change from solid to liquid Next Slide Boiling : change from liquid to gas Solidifying : change from liquid to solid Condensing : change from gas to liquid States 1

3. States Latent heat of fusion Certain amount of energy is absorbed when a substance changes from solid to liquid without a change of temperature. The same amount of energy is released when the substance changes from liquid to solid without a change of temperature. This amount of energy is called the latent heat of fusion. Next Slide States 2

4. States Latent heat of vaporization Next Slide Certain amount of energy is absorbed when a substance changes from liquid to gas without a change of temperature. The same amount of energy is released, when the substance changes from gas to liquid without a change of temperature. This amount of energy is called the latent heat of vaporization. States 3

5. States Internal energy and States Internal energy : sum of K.E. and P.E. of all particles Next Slide K.E. : the energy of vibrations of the particles P.E. : intermolecular forces among the molecules K.E, P.E. and states Specific latent heat of substances : the amount of energy required to change the state of a substance with a mass 1 kg without a change in temperature Diagram States 4

6. States Experiment Experiment to find the specific latent heat of fusion of ice Next Slide Diagram Experiment to investigate the change of state Diagram Heating curves and cooling curves Diagram Example Diagram States 5

7. States Evaporation and applications Evaporation : Next Slide Differences between evaporation and boiling Diagram Examples of latent heat Photo Liquid changes to gas at a temperature below the boiling point States 6

8. END of Change of State

9. States Click Back to gas liquid solid gain in K.E. gain in P.E.: latent heat of vaporization gain in P.E.: latent heat of fusion Back to States 4

10. States Next Slide We use the following set-up to investigate the specific latent heat of vaporization. control apparatus experimental apparatus Joulemeter (or kilo-watt hour meter) water melted by the heat from the surroundings water melted by the heat from the surroundings + heater States 5

11. States Click Back to Back to Mass of experimental cup + water = 0.045 kg Mass of control cup + water = 0.014 kg Mass of water melted by heater only = (0.045  0.014) kg = 0.031 kg Initial Joulemeter reading = 15600 J Final Joulemeter reading = 29800 J Energy supplied = (29800  15600) J = 14200 J Specific latent heat of fusion of ice = (14200  0.031) J/kg = 458000 J/kg States 5

12. States Next Slide Some wax is placed in a test-tube with a thermometer. The test-tube is heated until the wax melts and becomes liquid and then the test-tube is left alone. The temperature vs time graph is plotted according to the data recorded. We find that the central part of the curve levels off. During that duration, the liquid changes back to solid, i.e. a change of state. States 5

13. States Click Back to Back to Experimental setup and the graph: temperature solid solid-liquid liquid melting point time wax in liquid form thermometer States 5

14. States Next Slide Heating curve : solid solid-liquid liquid liquid-gas gas boiling point melting point time temperature States 5

15. States Click Back to Back to Cooling curve : solid solid-liquid liquid liquid-gas gas boiling point melting point temperature time States 5

16. States Next Slide What is the energy required to change a 2 kg block of ice at 0  C to steam at 100  C? (specific heat capacity of water : 4200 J/(  Ckg) specific latent heat of fusion : 336000 J/kg specific latent heat of vaporization : 2280000 J/kg) States 5

17. States Click Back to Back to States 5

18. States Click Back to Back to EvaporationBoiling Occurs at any temperature Occurs at a definite temperature: the boiling point Occurs at the surfaceOccurs within the liquid No bubblesBubbles appear States 6

19. States Next Slide Sweating : evaporation of sweat carries heat away from the body States 6

20. States Next Slide Refrigerator : Freon evaporates inside a refrigerator and carries away some heat. At the back of the refrigerator, freon vapour condenses and releases the heat. States 6

21. States Click Back to Back to You feel cold when you are out of a swimming pool in winter, though it is warm when you are in the swimming pool. States 6