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Chapter 13 Phase Changes. Notes #6b. 13.4 Phase Changes. Phase changes that REQUIRE energy Melting – ice is an example: heat is transferred to the ice, which breaks some of the hydrogen bonds.
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Chapter 13Phase Changes Notes #6b
13.4 Phase Changes • Phase changes that REQUIRE energy • Melting – ice is an example: heat is transferred to the ice, which breaks some of the hydrogen bonds. • Melting Point – the temperature at which the forces holding its crystal lattice together are broken and it becomes a liquid. • Vaporization – the process by which a liquid changes to a gas of vapor. • Evaporation – vaporization that occurs only at the surface of a liquid. This is how our bodies regulate temperature.
13.4 Phase Changes • Phase changes that REQUIRE energy • vapor pressure – pressure exerted by a vapor over a liquid • boiling point – the temperature at which the vapor pressure of a liquid equals the external or atmospheric pressure. • Sublimation – process by which a solid changes directly to a gas without first becoming a liquid -(dry ice).
13.4 Phase Changes • Phase changes that RELEASE energy • Condensation – process by which a gas or vapor becomes a liquid (reverse of vaporization.) • Deposition – process by which a substance changes from gas or vapor to a solid (reverse of sublimation.) • Freezing– reverse of melting • Freezing Point – temperature at which a liquid is converted into a crystalline solid.
13.4 Phase Changes • Phase diagrams