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

Heating & Cooling CurvesDo Now: Name the phase changeS  LL  GG  LL  SS  GG  S Melting (fusion) Boiling (vaporization) condensation Freezing (solidification) sublimation 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 ! We can see these energy changes by looking at a heat/cooling curve – next slide Endothermic Sublimation Vaporization Melting (fusion) Deposition Condensation Freezing (solidification) Gas PE Liquid Solid Exothermic

TURN TO PACKET page 11, take notes here:

I II K.E.↔ III IV V Liquid & Gas Gas Solid & Liquid Liquid Solid ● Boil pt. Temperature Melt pt. ● K.E. K.E. K.E.↔ K.E. P.E.↔ P.E. P.E. P.E.↔ P.E.↔ Time

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?

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