Second Law of thermodynamics

how can something become more stable

lower energy/enthalpy

higher spreading energy/entropy

entropy

measures how energy spreads

related to various modes of motion in a molecule+randomness of a system

how does entropy relate to physical states

increased entropy increases w/ increasing freedom of motion of molecules

rules for determining entropy

1. phase - s<l«<g

2. amount of matter - more particles → more entropy

3. temperature - higher temp → higher entropy

4. volume of gasses only

5. structure of matter - as particle sizes increases, entropy increases

how does temp hellp determine entropy

particles can be arranged more diversely when temp is higher

how does structure of matter determine entropy

larger particles → more bonds → can store energy in more ways

entropy at 0K

0

molar entropy

entropy of one mol of something

units of molar entropy

J/K mol

standard entropy

S° measured under standard conditions

what type of rxn is entropy of a rxn

a state rxn

ΔS°

difference in randomness of reactions compraed to products

units of ΔS°

J/Kmolrxn

second law of thermodynamics

the total entropy (disorder) of an isolated system always increases over time

ΔS_system+ΔS_surroundings>0

system+surroundings must go up

Changes in entropy of surroundings

• When a process releases heat to the surroundings, the surroundings’ entropy increases (energy spreads out).

• When a process absorbs heat from the surroundings, the surroundings’ entropy decreases (energy becomes less spread out).

temp dependence of ΔS_surr

• Higher temperature → smaller change in ∆Sₛᵤᵣᵣ

  • Lower temperature → bigger change in ∆Sₛᵤᵣᵣ

relative entropy by molar mass

relative entropy generally increases with molar mass