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States 1

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

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States 1

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

  2. States States 2 Next Slide 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.

  3. States States 3 Next Slide Latent heat of vaporization • 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.

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

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

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

  7. END of Change of State

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

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

  10. Back to States States 5 Click 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

  11. States States 5 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.

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

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

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

  15. States States 5 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)

  16. Back to States States 5 Click Back to

  17. Evaporation Boiling Occurs at any temperature Occurs at a definite temperature: the boiling point Occurs at the surface Occurs within the liquid No bubbles Bubbles appear Back to States States 6 Click Back to

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

  19. States States6 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.

  20. Back to States States 6 Click 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.

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