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This guide provides a comprehensive overview of heat exchange calculations in physical processes, focusing on the use of the equation Q = m(Hf) for phase changes such as melting and freezing. It covers key concepts like temperature changes (∆T), heating and cooling processes, and distinctions between heat evolved and heat absorbed. Additionally, it explains how to identify hints for phase change scenarios and provides insights on constant temperatures at freezing and boiling points. This resource is essential for students and professionals dealing with thermodynamics.
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PHYSICAL PROCESS q EQUATIONS DECISION MAP PHYSICAL PROCESS HEAT EXCHANGE (q) CALCULATION Q = mHf. Hf = HEAT OF FUSION TABLE B • RECOGNIZE HINTS • A ∆T. • 2 TEMPERATURES GIVEN • ONE TEMP GIVEN AND ONE ASKED FOR. • HEATING • COOLING • HEAT EVOLVED • HEAT ABSORBED • HOW MANY J OR kJ need to cause a certain ∆T. NO IS THERE A PHASE CHANGE ? • RECOGNIZE HINTS • NO ∆T. • FREEZING • MELTING • SOLID TO LIQUID, LIQUID TO SOLID • AT 0.0 C (WATER) • CONSTANT TEMP • AT FREEZING YES YES Use Q = mC∆T. ∆T = T2 – T1 IS THE SAMPLE AT THE FREEZING POINT NO
RECOGNIZE HINTS • NO ∆T. • CONDENSATION • EVAPORATION • LIQUID TO GAS, GAS TO LIQUID • AT 100 C (WATER) • CONSTANT TEMP • AT BOILING POINT Q = mHV HV = HEAT OF VAPORIZATION TABLE B
