Changes of StateChanges of State

Prentice-Hall Chapter 13.4Prentice-Hall Chapter 13.4Dr. YagerDr. Yager

ObjectivesObjectives

IdentifyIdentify the conditions necessary for sublimation. the conditions necessary for sublimation.

DescribeDescribe how equilibrium conditions are how equilibrium conditions are represented in a phase diagram.represented in a phase diagram.

Four States of MatterFour States of Matter

Solid Solid Liquid Liquid Gas or Vapor Gas or Vapor PlasmaPlasma

Changes in StateChanges in State

Solid to Liquid – MeltingSolid to Liquid – Melting Liquid to Gas – Boiling, evaporationLiquid to Gas – Boiling, evaporation Vapor to Liquid – CondensationVapor to Liquid – Condensation Liquid to Solid – FreezingLiquid to Solid – Freezing Solid to Vapor – SublimationSolid to Vapor – Sublimation Vapor to Solid – DepositionVapor to Solid – Deposition Vapor to Plasma – Hot, Hot, Hot!!!Vapor to Plasma – Hot, Hot, Hot!!!

SublimationSublimation

sublimationsublimation: the change in state from solid to : the change in state from solid to vapor without passing through the liquid statevapor without passing through the liquid state

Sublimation occurs in solids with vapor pressures Sublimation occurs in solids with vapor pressures that exceed atmospheric pressures at or near that exceed atmospheric pressures at or near room temperature.room temperature.

When solid iodine is heated, the crystals sublime, going directly from the solid to the gaseous state.

When the vapor cools, it goes directly from the gaseous to the solid state.

Uses of SublimationUses of Sublimation

Dry Ice - keep ice cream frozenDry Ice - keep ice cream frozen

Freeze Dried Coffee - vacuum pump over iceFreeze Dried Coffee - vacuum pump over ice

Solid Air FreshenersSolid Air Fresheners

Separation of materials by organic chemistrySeparation of materials by organic chemistry

Phase DiagramsPhase Diagrams phase diagramphase diagram: a graph which shows the : a graph which shows the

relationship among solid, liquid and gasrelationship among solid, liquid and gas

The two axes for a fixed volume are pressure The two axes for a fixed volume are pressure (y-axis) and temperature (x-axis). (y-axis) and temperature (x-axis).

Key IdeaKey Idea

When two phases exist in equilibrium they are When two phases exist in equilibrium they are indicated on a phase diagram by a line indicated on a phase diagram by a line separating the phases.separating the phases.

The triple point describes the only set of conditions at which all three phases can exist in equilibrium with one another.

For water this occurs at 0.016oC and 0.61 kPa.

Phase Diagram of COPhase Diagram of CO22

Why Does Ice Float?Why Does Ice Float?

1.1. Identify the change of state that Identify the change of state that occurs when solid COoccurs when solid CO22 changes to changes to

COCO22 gas as it is heated. gas as it is heated.

a.a. condensationcondensation

b.b. freezingfreezing

c.c. vaporizationvaporization

d.d. sublimationsublimation

1.1. Identify the change of state that Identify the change of state that occurs when solid COoccurs when solid CO22 changes to changes to

COCO22 gas as it is heated. gas as it is heated.

a.a. condensationcondensation

b.b. freezingfreezing

c.c. vaporizationvaporization

d.d. sublimationsublimation

2. Sublimation occurs in solids if the vapor 2. Sublimation occurs in solids if the vapor pressure at or near room temperature pressure at or near room temperature

a.a. exceeds atmospheric pressure.exceeds atmospheric pressure.

b.b. equals atmospheric pressure.equals atmospheric pressure.

c.c. is less than atmospheric pressure.is less than atmospheric pressure.

d.d. is less than half the atmospheric pressure.is less than half the atmospheric pressure.

2. Sublimation occurs in solids if the vapor 2. Sublimation occurs in solids if the vapor pressure at or near room temperature pressure at or near room temperature

a.a. exceeds atmospheric pressure.exceeds atmospheric pressure.

b.b. equals atmospheric pressure.equals atmospheric pressure.

c.c. is less than atmospheric pressure.is less than atmospheric pressure.

d.d. is less than half the atmospheric pressure.is less than half the atmospheric pressure.

3. What is the significance of a line in a 3. What is the significance of a line in a phase diagram?phase diagram?

a.a. Only one phase is present.Only one phase is present.

b.b. Two phases are in equilibrium.Two phases are in equilibrium.

c.c. Three phases are in equilibrium.Three phases are in equilibrium.

d.d. The distinction between two phases The distinction between two phases

disappears.disappears.

3. What is the significance of a line in a 3. What is the significance of a line in a phase diagram?phase diagram?

a.a. Only one phase is present.Only one phase is present.

b.b. Two phases are in equilibrium.Two phases are in equilibrium.

c.c. Three phases are in equilibrium.Three phases are in equilibrium.

d.d. The distinction between two phases The distinction between two phases

disappears.disappears.

4. What is the significance of the triple 4. What is the significance of the triple point in a phase diagram?point in a phase diagram?

a.a. Temperature and pressure are equal.Temperature and pressure are equal.

b.b. Two phases are in equilibrium.Two phases are in equilibrium.

c.c. Three phases are in equilibrium.Three phases are in equilibrium.

d.d. The distinction among three phases The distinction among three phases

disappears.disappears.

4. What is the significance of the triple 4. What is the significance of the triple point in a phase diagram?point in a phase diagram?

a.a. Temperature and pressure are equal.Temperature and pressure are equal.

b.b. Two phases are in equilibrium.Two phases are in equilibrium.

c.c. Three phases are in equilibrium.Three phases are in equilibrium.

d.d. The distinction among three phases The distinction among three phases

disappears.disappears.