Prentice-Hall Chapter 13.4 Dr. Yager Changes of State Prentice-Hall Chapter 13.4 Dr. Yager

Objectives Identify the conditions necessary for sublimation. Describe how equilibrium conditions are represented in a phase diagram.

Four States of Matter Solid Liquid Gas or Vapor Plasma

Changes in State Solid to Liquid – Melting Liquid to Gas – Boiling, evaporation Vapor to Liquid – Condensation Liquid to Solid – Freezing Solid to Vapor – Sublimation Vapor to Solid – Deposition Vapor to Plasma – Hot, Hot, Hot!!!

Sublimation sublimation: the change in state from solid to vapor without passing through the liquid state Sublimation occurs in solids with vapor pressures that exceed atmospheric pressures at or near 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 Sublimation Dry Ice - keep ice cream frozen Freeze Dried Coffee - vacuum pump over ice Solid Air Fresheners Separation of materials by organic chemistry

Phase Diagrams Key Idea phase diagram: a graph which shows the relationship among solid, liquid and gas The two axes for a fixed volume are pressure (y-axis) and temperature (x-axis). Key Idea When two phases exist in equilibrium they are indicated on a phase diagram by a line 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 CO2

Why Does Ice Float?

Identify the change of state that occurs when solid CO2 changes to CO2 gas as it is heated. condensation freezing vaporization sublimation

Identify the change of state that occurs when solid CO2 changes to CO2 gas as it is heated. condensation freezing vaporization sublimation

2. Sublimation occurs in solids if the vapor pressure at or near room temperature exceeds atmospheric pressure. equals atmospheric pressure. is less than atmospheric pressure. is less than half the atmospheric pressure.

2. Sublimation occurs in solids if the vapor pressure at or near room temperature exceeds atmospheric pressure. equals atmospheric pressure. is less than atmospheric pressure. is less than half the atmospheric pressure.

3. What is the significance of a line in a phase diagram? Only one phase is present. Two phases are in equilibrium. Three phases are in equilibrium. The distinction between two phases disappears.

3. What is the significance of a line in a phase diagram? Only one phase is present. Two phases are in equilibrium. Three phases are in equilibrium. The distinction between two phases disappears.

4. What is the significance of the triple point in a phase diagram? Temperature and pressure are equal. Two phases are in equilibrium. Three phases are in equilibrium. The distinction among three phases disappears.

4. What is the significance of the triple point in a phase diagram? Temperature and pressure are equal. Two phases are in equilibrium. Three phases are in equilibrium. The distinction among three phases disappears.