Topic: Heating Curves for pure substance

Do Now: What is the difference between a mixture and a pure

substance?

Review: Name the phase changeS LL GG LL SS GG S

Melting (fusion)

Boiling (vaporization)condensation

Freezing (solidification)

sublimationdeposition

REVIEW: All Phase changes accompanied by energy changes

B

D E

C B

E D

MELTING

Vaporization(boiling)

FREEZING

Condensation

EXO EXO

ENDO

ENDO

Time

Tem

pera

ture

IV V

Solid

Solid & Liquid

Liquid

Liquid & Gas

Gas

K.E.

K.E. K.E.K.E.↔ K.E.↔P.E.↔

P.E.↔ P.E.↔P.E. P.E.

Melt pt.

Boil pt.

●

●

Time

Tem

pera

ture

I II III IV V

Solid

Solid & Liquid

Liquid

Liquid & Gas

Gas

K.E.

K.E. K.E.K.E.↔ K.E.↔P.E.↔

P.E.↔ P.E.↔P.E. P.E.

Melt pt.

Boil pt.

●

●

Freezing pt. ●

B

D E

C B

E D

MELTING

Vaporization(boiling)

FREEZING

Condensation

Melting point/Freezing Point

Boiling Point

Melting & Boiling Points (start of the phase change)

• Plateaus = Phase changes = PE changes

– always given as temp (˚C, K)

• WHY IS IT CALLED A POINT?

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

QUICK QUESTION:What happens to temperature as heat is added to boiling water?

• Nothing, temp doesn't’t change b/c 2 phases are present– temp will change when only 1 phase

is present!

PAGE 13 answer 3-83. MP = _________ BP=_______7. When is the kinetic energy of the sample the greatest?

8. Given a constant heating rate of 150 Joules per minute, how many joules of heat must the sample absorb to melt all of the sample?

To vaporize all of the sample?

GAS phase

150 J 9 minutes = 1350 Joules

minute

150 J 30 minutes = 4500 Joules

minute

9 30

70 °C 150 °C

What do you think a cooling curve would look like?