Thermodynamics Part 1

Slide 1

Introduction to Thermodynamics
Thermodynamics = science of the interconversion  of different forms of ENERGY (ex/ heat, mechanical work, chemical energy)                    -> Chemical reactions involve a transfer of energy between the system and surroundingSystem = the part of the universe under observation          -> The System can be:               a) "open" - both mass & energy may leave and enter (i.e. beaker)              b) "closed" - energy can be exchanged but no mass can enter/leave (i.e. sealed flask)              c) "isolated" - neither mass nor energy may enter/leave (i.e. insulated, closed container) Surroundings = the rest of the universeTherefore, the "universe" is made up of the ""System" and the "Surroundings" The "STATE" of a system is characterized by a set of variables (i.e. P, V, T, n, etc.)These are STATE VARIABLES.           -> P, V, T, n and mass can be classified as either:              * Intensive - independent of size (ex/ P, T, etc.)              * Extensive - dependent of size (ex/ mass, V, n, etc.) We can transfer energy in and out of a system, where the INTERNAL ENERGy  of the system may change

Slide 2

Introduction to Thermodynamics
Internal Energy (U) = the sum of the kinetic and potential energy of system Two ways U can change:1. Heat (q)2. Work (w)*another way is by adding/removing mass but this is not encountered in a "closed" systemWe can only measure changes in U, not absolute values so for any reaction/process, U(final) - U(initial) = delta U***1st Law of Thermodynamics => delta U = q + w (statement from the conservation of energy)The Law of Conservation of Energy states energy may be converted from one form to another, but the total quantity of energy remains constantHEAT ENERGY, HEAT TRANSFER and TEMPERATUREdelta U = q + w tells us we cannot create/destroy energy, but it can be transferred in and out of the system

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