The document discusses different types of phase changes: 1) Evaporation is when liquid changes to gas as molecules gain kinetic energy and leave the surface. Boiling is evaporation occurring within the liquid as bubbles form. 2) Condensation is the opposite, when gas changes to liquid as high energy gas molecules hit the liquid surface. 3) Melting is when a solid changes to a liquid as heat is absorbed and molecules vibrate more. Freezing is the reverse as energy is removed and molecules slow down. 4) Sublimation and deposition involve direct changes between solid and gas phases.

1. Agenda
Bell work
• Pass in Lab Reports
• Notes: Change of
Phase
• States of Matter Phet
Simulation
• Define Specific Heat
Capacity
• Distinguish between High
and Low Specific Heat.
• Give an example of each
• How does water’s Specific
heat control earth’s climate
• What is special about
Islands and Peninsula's?

3. Change of Phase
March 14, 2013

4. Objectives
1.
Explain changes in phase according to
heat and energy
2.
Define each of the phase changes

5. Heat Transfer
 When matter changes phase, a transfer of
thermal energy is involved

6. Evaporation
Liquid changes to gas
 Molecules that gain
kinetic energy at the surface
get bumped free
 Becomes gas phase above
the liquid

7. Evaporation
 Molecules that leave the liquid have the
most energy
 Energy of the liquid decreases
 Temperature of the liquid goes down
 EX. Perspiration

9. Would evaporation be a cooling process if
there were no transfer of molecular energy
from water to the air above?

10. Boiling
 Evaporation occurring within a liquid as
well as its surface
 Bubbles of vapor form
in the liquid and are
buoyed to the surface,
where they escape

11.  Boiling like evaporation is a cooling
process
 Boiling water is in thermal equilibrium
 It is being cooled by
boiling as fast as it
is being heated by
energy from the
heat source

12. Since boiling is a cooling process, would it
be a good idea to cool your hot, sticky
hands by dipping them into boiling water?

13. Condensation

Gas to a Liquid

High energy molecules close to the surface
become attracted to the liquid

Hit the surface with increased kinetic energy

Raising the temperature of the water

Gas has a lot of energy to give up

15. If the water level in a dish of water remains
unchanged from one day to the next, can
you conclude that no evaporation or
condensation is taking place?

16. Melting and Freezing
Melting - solid to a liquid
 heat is absorbed the molecules vibrate
more and more breaking the attractive
forces

17. Freezing - liquid to a solid
 energy is taken from the liquid, molecular
motion slows down
 attractive forces between
them bind them together

18. Sublimation
 Molecules jump directly from
solid phase
to gaseous phase
 Snow and ice melting on a hot sunny day
 Dry ice in air

19. Deposition
 Molecules jump directly from
solid phase
 Snow forming
high in the
atmosphere
gas phase to