The First Law of Thermodynamics q > 0 for heat flow ______ the system w > 0 for work done ______ the system For ________ changes of state: For ________ changes: U is the ________ energy of the system. When a system changes from one state to another along an ________ path, the amount of work done is the same, whatever the means employed: i.e. for but for The energy of an ________ system is constant. For  No perpetual motion machines! In any cyclic transformation the work done by a system on its surroundings is equal to the ________ withdrawn from the surroundings. The energy of the universe is ________ . Modified by Jed Macosko 11/26/2018

Modified by Jed Macosko Temperature Two systems in thermal equilibrium are at the same ________ . If system A is in thermal equilibrium with system B, and A is in thermal equilibrium with C, then B must be in thermal equilibrium with C. This is a statement of the ________ law of thermodynamics. _______ temperature: when Unit of temperature: The freezing point in the presence of air, and at 1 atm is 0.01 °C lower than the triple point, because of air solution and increased pressure. The freezing point of water at 1 atm is 273.15 K. The boiling point of water at 1 atm is 373.12 K. Why not 373.15? The Celsius scale is defined as It is possible to define an ________ temperature scale (Kelvin scale) by considering (next slides) the work done in an isothermal ________ expansion/compression… This absolute T is the scaling factor that relates volume change to work. Modified by Jed Macosko 11/26/2018

Modified by Jed Macosko Pressure–Volume Work 1 T1,P1,V1 m T2,P2,V2 h A = area of piston Expansion P1 P2 V1 V2 1 2 equation of state (need not be _______) Expansion into a _______ P2 P1 V2 V1 1 2 Compression Modified by Jed Macosko 11/26/2018

Modified by Jed Macosko Pressure–Volume Work 2 Multi-stage Expansion P 1 5 3 2 4 _______Expansion Make steps so small that P 1 2 For _______gases and at fixed temperature Modified by Jed Macosko 11/26/2018

Modified by Jed Macosko Pressure–Volume Work 3 P 1 3 4 ______________ ______________ 2 Consider the cyclic path 1  2  3  4  1 Consider the cyclic reversible path 1  3  1 Even for a cyclic process w depends on _______ Modified by Jed Macosko 11/26/2018

Modified by Jed Macosko Energy vs. Enthalpy For a change in state at constant volume, no expansion work is done, so However, for a change in state at constant pressure, P constant _______ H, being a function of _______ variables only, is also a _______ variable. For a general change of state (P and V may both change), Modified by Jed Macosko 11/26/2018

Modified by Jed Macosko Heat _______ Transfer of heat to a system may result in a rise in T. path function, so C depends on conditions. Define: at constant volume, no work at constant pressure, only ______ work From 1st Law, assume no ____ _______ Similarly For _______ Modified by Jed Macosko 11/26/2018

The Relation Between CP and CV But since work needed to overcome _____________ forces expansion per degree “_______ pressure” For ideal gases For liquids and solids is so small that Modified by Jed Macosko 11/26/2018

Modified by Jed Macosko Adiabatic Expansion 1 _______ = insulated: For adiabatic expansion Free expansion: Fixed pressure: _______ expansion: Substitute appropriate equation of state. Not useful if ____ changes. Modified by Jed Macosko 11/26/2018

Modified by Jed Macosko Adiabatic Expansion 2 Reversible adiabatic expansion of _______ ______: ideal gases only P V2 V1 Also, since Modified by Jed Macosko 11/26/2018

Types of Expansion Work ― Summary For _______ _______ of expansion For _______ changes in general In an _______ expansion For _______ expansions T is held constant by leakage of heat into the system from the surroundings. For an ideal gas so the internal energy must provide for the work: In an _______ expansion For _______ expansion of _______ _______ through a given volume change from the same initial state, since U is continuously replenished by heat intake to keep the temperature constant. Modified by Jed Macosko 11/26/2018