ChemExam3StudyGuide - b p m p tempera ture heat added...

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b p m p tempera ture heat added change state (PE) increase temp (KE) ? Hf us ? Hv ap ga s T increasing= change in KE Change of state= change in PE Topic 17 Pre-Class Six conversion processes between three states of matter. Melting- solid to liquid Freezing- liquid to solid Evaporation- liquid to gas Condensation- gas to liquid Sublimation- solid to gas Deposition- gas to solid Energies of Phase Changes: Heat of fusion H (? fus )- amount of energy required to melt 1 mol of solid material Heat of vaporization H (? vap )- amount of energy required to vaporize 1 mol of liquid material Heat of sublimation H (? sub )- amount of energy required to sublime 1 mol of solid material Adding Heat Solid state + heat= increase in temp until reaches melting point. + More heat= solid to liquid conversion (melting) without a temp change. Liquid state + heat= increase in temp until reaches boiling point. + More heat= liquid to gas conversion (boiling) without a temp change. **continuing to add heat to gas will increase temp. Energies and Forces Material with weak forces → doesn’t take much energy to pull molecules apart, so relatively low BP and relatively small H ? vap . Material with strong forces → takes a lot of energy to pull molecules apart, so relatively high BP and relatively large H ? vap . **BP and H ? vap not directly proportional, but we expect them to trend the same way. Kinetic vs. Potential Energy Addition of heat causes increase in energy of that material. That added energy manifests itself as a change in the material’s kinetic or potential energy. We associate KE with motion of molecules. Average speed of molecules and average KE of materials increases with temp. We associate PE with position of molecules relative to one another. In going from solid to liquid state, or liquid to gas state, those relative positions change, resulting in a change in the PE of the material. Vapor Pressure:
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While water vapor builds up, condensation starts to occur. This eventually reaches an equilibrium, where the rates of evaporation and condensation are equal.
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