Energy and chemistry Net transfer of thermal energy stops when two objects reach same temp Energy capacity to do work w or transfer of heat q Heat thermal energy that can be transferred from an object at one temperature to an object at another temperature Other types of energy Radiant light energy in light microwaves and radio waves Thermal kinetic and potential results from atomic and molecular motion temperature of an object is measure of thermal energy content Chemical results from particular arrangement of atoms in chemical compound Nuclear nucleus in atoms Electrical transfer or ow of electrons Potential and kinetic energy Potential energy energy stored in an object because of the relative positions or orientations Kinetic energy 1 2 mass x velocity 2 Energy of a motion E h nu nu c wavelength Internal energy E Number of particles Type of particles solid liquid gas Temp PE KE Depends on Higher the T the higher the internal energy Changes in T monitor changes in E Change in E q w Heat transfer in endothermic q Heat transfer out exothermic q W transfer in w surroundings does work on system W transfer out w system does work on surroundings law of conservation Total energy is unchanged in chemical reaction If PE of products is less than reactants the difference must be released as KE Thermodynamics enthalpy Heat transfers until thermal equilibrium is established Delta T measures energy transferred System object under study Open can exchange both matter and energy w surroundings Closed can exchange energy but not matter w surroundings Isolated system exchanges neither energy nor matter w surroundings total energy of system plus surroundings is constant Surroundings everything outside system First law of thermodynamics Change in energy q w Chemical systems tend toward state of min PE Chem systems tend toward state of max disorder State of a system State of system is complete description of system at given time including temp and pressure amt of matter it contains chem composition and physical state of the matter Sum change in enthalpy along one path sum change in enthalpy along another path Ex Temp pressure volume change in energy change in enthalpy entropy Non state functions moles heat work Standard states and standard enthalpy changes Thermochemical standard T 298 15 K Thermochemical standard P 1 0000 atm For pure substances in their liquid or solid phase the standard state is the pure liquid or solid For gasses the standard state is the gas at 1 00 atm of pressure
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