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Changes of State 13.4 • 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.
13.2 A Model for Liquids • A Model for Liquids • What factors determine the physical properties of a liquid?
13.2 A Model for Liquids • Substances that can flow are referred to as fluids. Both liquids and gases are fluids.
13.2 A Model for Liquids • The movement of particles in a liquid and the attractions among the particles determines the physical properties of liquids.
13.2 Evaporation • The conversion of a liquid to a gas or vapor is called vaporization. • When such a conversion occurs at the surface of a liquid that is not boiling, the process is called evaporation.
13.2 Evaporation • In an open container, molecules that evaporate can escape from the container.
13.2 Evaporation • In a closed container, the molecules cannot escape. They collect as a vapor above the liquid. Some molecules condense back into a liquid.
13.2 Vapor Pressure • Vapor pressure is a measure of the force exerted by a gas above a liquid.
13.3 A Model for Solids • A Model for Solids • How are the structure and properties of solids related?
13.3 A Model for Solids • The general properties of solids reflect the orderly arrangement of their particles and the fixed locations of their particles.
13.3 A Model for Solids • The melting point (mp) is the temperature at which a solid changes into a liquid.
13.4 Sublimation • Sublimation • When can sublimation occur?
13.4 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.
13.4 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.
13.1 Kinetic Theory and a Model for Gases • Kinetic Theory and a Model for Gases • What are the three assumptions of the kinetic theory as it applies to gases?
13.1 Kinetic Theory and a Model for Gases • According to kinetic theory: • The particles in a gas are considered to be small, hard spheres with an insignificant volume. • The motion of the particles in a gas is rapid, constant, and random. • All collisions between particles in a gas are perfectly elastic.
13.1 Gas Pressure • A barometer is a device that is used to measure atmospheric pressure.
13.1 Gas Pressure • The SI unit of pressure is the pascal (Pa). • One standard atmosphere (atm) is the pressure required to support 760 mm of mercury in a mercury barometer at 25°C.
13.4 Phase Diagrams • Phase Diagrams • How are the conditions at which phases are in equilibrium represented on a phase diagram?
13.4 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).
13.4 Phase Diagrams
13.4 Phase Diagrams • The triple point describes the only set of conditions at which all three phases can exist in equilibrium with one another.
13.4 Section Quiz. • 13.4.
13.4 Section Quiz. • 1. Identify the change of state that occurs when solid CO2 changes to CO2 gas as it is heated. • condensation • freezing • vaporization • sublimation
13.4 Section Quiz. • 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.
13.4 Section Quiz. • 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.
13.4 Section Quiz. • 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.
Concept Map 13 • Solve the Concept Map with the help of an interactive guided tutorial.
