Transcript Heating & Cooling Curves Do Now: Name the phase change S  L

Heating & Cooling Curves
Do Now:
Name the phase change
S  L Melting (fusion)
L  G Boiling (vaporization)
G  L condensation
L  S Freezing (solidification)
S  G sublimation
G  S deposition
All Phase changes accompanied by
energy changes
• Phase changes are physical changes:
– sometimes energy is absorbed (endothermic)
– sometimes energy is released (exothermic)
• Energy change for given phase change
can be measured/calculated (we’re going
to learn how to do this tomorrow)
• As you go from S  L  G, you are
increasing the distance between molecules, so
you are increasing their PE !
Endothermic
Gas
PE
Sublimation
Deposition
Vaporization
Condensation
Melting
(fusion)
Freezing
(solidification)
Liquid
Solid
Exothermic
We can see these energy changes by looking at a heat/cooling curve – next slide
TURN TO PACKET page 11,
take notes here:
Temperature
I
II
Solid
Solid &
Liquid
III
IV
Liquid
& Gas
Liquid
V
Gas
●
Boil pt.
Melt pt.
K.E.
P.E.↔
●
K.E.↔
P.E.
K.E.
P.E.↔
Time
K.E.↔
P.E.
K.E.
P.E.↔
During Phase changes
• More than one phase is present
– Melting : solid and liquid
– Boiling: liquid and gas
(lets check out a tiger animation)
• temperature is constant: T=0
–There is no change in temp!!!!!
***NOTE: if 2 phases are present,
temp is constant
Melting & Boiling Points
• Plateaus = Phase changes = PE changes
– always given as temp (˚C, K)
• WHY IS IT CALLED A POINT?
QUICK QUESTION:
What happens to temperature as
heat is added at boiling point?
• Nothing, temp doesn't’t change
until only 1 phase is present!
What do you think a cooling
curve would look like?