# AUGUSTANA PH 202 - First Law of Thermodynamics (21 pages)

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## First Law of Thermodynamics

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- Pages:
- 21
- School:
- Augustana College - IL
- Course:
- Ph 202 - Basic Physics II

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First Law of Thermodynamics Physics 202 Professor Lee Carkner Lecture 11 PAL 10 Temperature How does the Galileo thermometer work The water in the tube changes density with T Water gets less dense as T rises and so the balls fall 64 to 80 Heat Al until it floats Need 1000 kg m3 so V m 2700 1000 2 7 V V DT T V V 1 7 1 6 9X10 6 24658 C Al would melt before getting to this temperature Heat Capacity Put a wooden spoon in a pot of water and boil it Heat capacity unit energy per degree temp is given by Q C Tf Ti C T Where Q heat J C is a property of a specific object Specific Heat C cm Where m is the mass and c is the specific heat Each type of substance has a c e g water iron etc Q cm Tf Ti Amount of heat Q needed to change the temperature of m kg of a certain type of substance from Ti to Tf Molar Specific Heat One mole 6 02 X 1023 atoms or molecules Q cmol of moles Tf Ti Used for gas Heat of Transformation Boiling water stays at 100 deg C the added energy goes into transforming the water from liquid to gas Q Lm Where L is the heat of transformation Vaporization and Fusion For the heat of For the heat of phase change from liquid to gas the vaporization LV is needed phase change from solid to liquid the fusion LF is needed The total heat necessary to change temperature and state is the sum of heats required for each Phase Curve for Water Calorimetry 1 Write out equation adding all heats in symbolic form and set equal to zero e g Q1 Q2 Q3 0 or m1c1 T1 m2L2 m3c3 T3 0 2 Substitute numbers use correct values for c and L 3 Make sure units for m c L and T match 4 Always use T Tf Ti don t add your own sign Temperature decrease results in a negative loss of heat 5 For Lm make positive if heat is absorbed and negative if heat is given of Solve for required variable Work and Internal Energy No heat can travel in or out If weight is removed from the piston head the remaining weight will rise Where does the energy come from It must come from the internal energy of the gas Internal

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