Lecture 9 Notes

H qp substancelosesorgainsebut tremainsconstant

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Unformatted text preview: motion against an opposing force. • constant V = no motion, so w = 0. At Constant P: ΔE = qP + watm= ΔH + watm • Subscript P shows fixed P. • watm = work done to push back the atmosphere • H = enthalpy. ΔH = qp • Substance loses (or gains) E, but… • T remains constant. Example: Convert ice at ‐50°C to water at +50°C Temperature (°C) ‐50 ‐25 0 25 50 Because ΔE = q + w: At Constant V: Freezing and Melting (Fusion) Ice is melting. T remains at 0°C Water warms from 0 to 50°C Ice warms from ‐50 to 0°C 0 100 200 300 400 500 600 Quantity of energy transferred (J) 1 2/2/2009 Changes of State ΔHfusion = qP = heat to melt a solid. Change Name value for H2O (J/g) s...
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