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

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 ! Gas PE Endotherm ic Sublimation Deposition Vaporization Condensation Melting (fusion) Freezing (solidification) Liquid Solid Exothermi We can see these energy changes by looking at a heat/coolingc curve – next slide

TURN TO PACKET page 11, take notes here:

II Temperatu re I III IV Liquid Solid Liqui & Gas & d Liquid Soli d Gas Boil pt. Melt pt. K.E. P.E. V 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?