1. THIS MEANS THAT
THINGS FALL.
THEY FALL FROM HEIGHTS OF
ENERGY AND STRUCTURED
INFORMATION INTO
MATTER IS ENERGY. MEANINGLESS, POWERLESS
DISORDER.
ENERGY IS INFORMATION.
EVERYTHING IS INFORMATION.
PHYSICS SAYS THAT
THIS IS CALLED
STRUCTURES... BUILDINGS,
SOCIETIES, IDEOLOGIES... ENTROPY.
WILL SEEK THEIR POINT OF
LEAST ENERGY.
Entropy (S) = a measure of randomness or disorder

2. Entropy
It’s just a measure of disorder
Physics classrooms are full of Entropy!

3. Entropy and your bedroom
Low Entropy High Entropy

4. No matter what we
say or try, the entropy
of the universe is
increasing!

5. The molecules in the solid are in a much more
restricted or ordered state so they have low
entropy.

6. Entropy increases when melting.
Entropy decreases when freezing

7. What happens to entropy when a machine does
work?
ΔS ↓
ΔS ↑

8. Refrigerators
Room
ΔS ↑
ΔS ↓
The heat pump in the fridge The entropy of the
does work to reduce the room increases by
entropy inside it. more.

9. What happens to the temperature of the
room?
The temperature
of the room
increases .

10. Entropy Increases with...
• Melting (fusion) Sliquid > Ssolid
• Vaporization Sgas > Sliquid
• Heating ST2 > ST1 if T2 > T1
• Dissolving (usually) Ssolution > (Ssolvent + Ssolute)
• Molecular complexity more bonds, more
entropy
• Atomic complexity more e-, protons,
neutrons

11. Entropy Curve
Solid Liquid Gas
S ← vaporization
Entropy
← fusion
0
0 Temperature (K)

12. The Statistics of Entropy
Another way to think about entropy is
that being disordered is just more
likely.
It’s just chance

13. A box containing air molecules, divided in two compartments
with a hole in the dividing wall. Since there are many more
molecules in the left compartment, there will also be many
more molecules crossing the divide from left to right.
The second law of thermodynamics states that in an isolated system
the entropy will increase.
In the statistical definition of entropy according to Boltzmann, this
means that the system will evolve to its most probable state.

14. Entropy, Marble Example
• Suppose you have a bag with 50 red
marbles and 50 green marbles
• You draw a marble, record its color, return
it to the bag, and draw another
• Continue until four marbles have been
drawn
• What are the possible results and what are
their probabilities?

15. Entropy, Marble Example,
Results
• The most ordered are the least likely
• The most disorder is the most likely

16. Entropy & Time
Because systems move from order to
disorder, time has a direction.

17. Which came first?

18. Entropy and Life
Life is an entropy reducer
Does this break the second law of thermodynamics?