Lecture 9 Notes

Lecture 9 Notes - States of Matter Solid Liquid Gas...

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2/2/2009 1 States of Matter: Solid - Liquid - Gas SOLID GAS LIQUID SUBLIMATION CONDENSATION FREEZING MELTING SUBLIMATION BOILING OR EVAPORATION DEPOSITION XXXXXXXXXXXX Conservation of Energy and Changes of State When heat is: Added to a system ± q is positive ± the change is endothermic Removed from a system ± q is negative ± the change is exothermic . Water Boils: H 2 O( l ) H 2 O(g) endothermic Steam Condenses: H 2 O(g) H 2 O( l ) exothermic Work occurs as the sample expands or contracts. Overall: Δ E = q + w A liquid cools from 45°C to 30°C, transferring 911 J to the surroundings. No work is done on or by the liquid. What is Δ E liquid ? Δ E liquid = q liquid + w liquid here w liquid = 0 Heat transfers from the liquid to the surroundings: q liquid = 911 J( q surroundings = +911 J) Δ E liquid = 911J Conservation of Energy and Changes of State A system does 50.2 J of work on its surroundings and there is a simultaneous 90.1 J heat transfer from the surroundings to the system. What is Δ E system ?
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Lecture 9 Notes - States of Matter Solid Liquid Gas...

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