Chemistry 17.4

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Chemistry 17.4

© Copyright Pearson Prentice Hall

Slide 2 of 17

Changes of State

Familiar weather events can remind you that water exists on Earth as a liquid, a solid, and a vapor. As water cycles through the atmosphere, the oceans, and Earth’s crust, it undergoes repeated changes of state. You will learn what conditions can control the state of a substance.

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Sublimation

Sublimation

When can sublimation occur?

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>Changes of State Sublimation

The change of a substance from a solid to a vapor without passing through the liquid state is called sublimation.

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

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>Changes of State Sublimation

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.

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Sublimation

Simulation 14

Predict the physical states present at different points on a phase diagram.


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Phase Diagrams

Phase Diagrams

How are the conditions at which phases are in equilibrium represented on a phase diagram?

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>Changes of State Phase Diagrams

A phase diagram is a graph that gives the conditions of temperature and pressure at which a substance exists as solid, liquid, and gas (vapor).

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Phase Diagrams

The conditions of pressure and temperature at which two phases exist in equilibrium are indicated on a phase diagram by a line separating the phases.

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>Changes of State Phase Diagrams13.4

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>Changes of State Phase Diagrams

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

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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

13.4 Section Quiz.

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Slide 13 of 17

13.4 Section Quiz.

1. Identify the change of state that occurs when solid CO2 changes to CO2 gas as it is heated.

a. condensation

b. freezing

c. vaporization

d. sublimation


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13.4 Section Quiz.

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

a. exceeds atmospheric pressure.

b. equals atmospheric pressure.

c. is less than atmospheric pressure.

d. is less than half the atmospheric pressure.


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

a. Only one phase is present.

b. Two phases are in equilibrium.

c. Three phases are in equilibrium.

d. The distinction between two phases disappears.

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

a. Temperature and pressure are equal.

b. Two phases are in equilibrium.

c. Three phases are in equilibrium.

d. The distinction among three phases disappears.

13.4 Section Quiz.


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Slide 17 of 17

Concept Map 13

Solve the Concept Map with the help of an interactive guided tutorial.

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Chemistry 17.4

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