1. States States 1 States Three states of matter : solid, liquid and gas
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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. Latent heat of fusion States 2 States
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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. Latent heat of vaporization
States
States 3
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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. Internal energy and States
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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 :
the amount of energy required to change the state of a substance with a mass 1 kg without a change in temperature

5. Experiment States 5 States
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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. Evaporation and applications
States
States 6
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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. Back to States 4 States Click Back to gas gain in K.E.
liquid
solid
gain in K.E.
gain in P.E.: latent
heat of vaporization
heat of fusion

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

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

11. States 5 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.

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

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

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

15. States 5 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 : J/kg
specific latent heat of vaporization : J/kg)

16. Back to
States
States 5
Click Back to

17. Back to States 6 States Click Back to 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

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

19. States 6 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.

20. Back to States 6 States 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.