Lecture 5 Flashcards
Energy transfer
work, heat, light or radiant
Internal transfer
chemical, nuclear, thermal, electrical energy
First law of thermodynamics
The law of conservation of energy. Energy cannot be created or destroyed just converted between forms
System
Includes a reaction and molecules involved. Can exchange mass and energy with surroundings
Surroundings
Everything else in the universe
Isolated thermodynamic system
No exchange of matter or energy
Closed thermodynamic system
Exchange of energy not matter
Open thermodynamic system
Exchange of both energy and matter
Change in enthalpy (Delta H)
ΔH = U + PV
ΔH = ΔH products - ΔH reactants
Hess’s law
overall reaction can be calculated by summing ΔH
Entropy (S)
a measure of uncertainty or randomness. More complex molecules increase the entropy
Order of entropy with different states
Ssolid < Sliquid < Sgas
When does entropy increase?
Melting, vapourizing, increasing S of solvent
Second law of thermodynamics
entropy of the universe increases with a spontaneous process
When is entropy spontaneous?
ΔS = > 0 Spontaneous
ΔS = 0 equilibrium
ΔS < 0 non-spontaneous
