thermodynamics Flashcards
closed vs. open system
closed system: exchange energy with outer environment
open system: exchange energy and matter with outer environment
1st law of thermodynamics
energy remains constant, only changes form (kinetic energy vs potential energy)
kinetic energy vs potential energy
kinetic: heat, pressure, motion
potential: bonds, gradients
enthalpy
energy content of bonds
-measure with change in heat in system from reactants –> products
change in enthalpy = change in heat = sum of heat of products - heat of reactants
enthalpy:
exothermic
endothermic
isothermic
exothermic: release heat (- change in heat) (usually spontaneous)
endothermic: absorb heat (+ change in heat) (non spontaneous)
isothermic: doesn’t release or absorb heat (zero change in heat)
2nd law of thermodynamics
more from order to disorder- entropy in universe always increases
entropy
how spread out (dispersed) energy is in a system
-increase entropy (s)= more dispersed
-i.e. a hot pan (concentrated energy) cools down (disperse energy into environment)
Gibbs free energy
energy difference between reactants and products
G = H - TS
H=enthlpy
T= temperature
S= entropy
-G= spontaneous, exergonic
+G= non spontaneous, endergonic
G=0 then at equilibrium
-depends on pH, temperature and concentration of reactants and products
standard Gibbs free energy
vs
non standard conditions
standard: 298k, pH=7, 1M of products and reactants
nonstandard: G= G* + RT ln [P]/[R]
- increase [R] = more exergonic (-G)
-increase [P] = more endergonic (+G)
-even if endergonic and large +G, if have lots more reactant then product then will be exergonic
spontaneous reaction (Gibbs, enthalpy and entropy)
-release heat (-H)
-increase entropy (+S)
- (-G)
enzymes
catalyst, dont change Gibbs free energy, decrease the activation energy (the energy to break bonds)
