Lecture 1 + 2, UNIT 1: FUNDAMENTAL PRINCIPLES & PARTICLES CH4 + 2O2 -> CO2 + 2H2O; reaction occurs with spark, gives off heat more energy -> less energy; less stable -> more stable thermodynamics: involves energy of reactants and products, not what happens in between (activation energy) & speed thermodynamics: involves the rate of reactions and activation barrier, how much energy put in to reach top of peak (temp) reaction mechanism: sequence of events to reassemble atoms in a reaction (making & breaking bonds); determines rate energy: ability of a system to do work by transforming from one state to another electrostatics: forces between charges (+and-, -and-, +and+) chemical energy: potential energy resulting from electrostatics 1 eV = 2.39 x 10⁻¹¹ cal = 6.70 x 10⁻²⁰ amu = 6.24 x 10¹⁸ eV CH4 + 2O2 -> CO2 + 2H2O + heat exothermic ΔE = -1000J, system lost energy E -> comes off (-1000J -> 0) ball with potential energy (↑) E = 0 (1000J -> 0) ball with negative potential energy endothermic ΔE = +1000J, system gained energy 1st law of thermodynamics: energy is conserved; Change in E = heat gained from/released into surroundings 2nd law of thermodynamics: entropy (natural dispersion of energy) of the universe is always increasing; energy does not come back easily; to break a bond, energy must be put in (ΔH = +) to form a bond, energy must be released (ΔH = -) ΔH = ΔE + PΔV at constant pressure, ΔH = ΔE + PΔV = ΔE + work natural cycles from low entropy -> high entropy ΔH = + increase in S drives to spontaneous ΔH = - ΔS = + (compensates for E needed to break bonds (H or E)) H2O (l) H2O (g) a reaction is spontaneous if it goes from TE -> HE or less thermodynamically stable to more thermodynamically stable (regardless of activation barrier height or reaction rate) is even if a spark is required to get over, speed up spontaneity determined by increasing entropy of the system and everything else, and lost heat to the surroundings. H-H + H-H -> H-H-H bonds made energy released ΔH = - (system) ΔS = + (surroundings) ΔS surroundings > ΔS system water molecules coming together free energy: release of energy (ΔH) enthalpy: release of heat (ΔH) free energy (G): energy usable to do work (ΔG) ΔG = ΔH - TΔS reaction spontaneous if ΔG < 0 ΔG = ΔH - TΔS T = temp (K) ΔH reflects chemical E, for most reactions, enthalpy dominates and reflects chemical E, ΔE/ΔH determines spontaneity! A chemical energy usually determines reaction spontaneity

CHEM 1810 - Lecture 1-2

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