Which way will it go: free energy decides

Science · Thermal & Statistical Physics · ages 20-22

Name ______________________ Date ____________

A process has negative delta G. What does that mean?
- It can run alone
- It must be driven
- It sits at equilibrium
Gibbs free energy G combines enthalpy H and entropy S at temperature T. How?
- H plus TS
- H over T
- H-TS
A spontaneous process always happens fast.
Circle one: True False
A process has delta G equal to zero. What does that mark?
- Impossible
- Instant
- Equilibrium
Ice refuses to melt in a freezer but melts in a warm room. Why?
- Enthalpy flips sign with heat
- T times delta S wins out
- Entropy shrinks when warmed
A process releases heat and gains disorder. When can it run on its own?
- Always
- Never
- Only when hot
A process absorbs heat yet still runs on its own. How is that possible?
- Heat flow direction reverses alone
- Work is always supplied secretly
- T times entropy beats heat cost
A mixed-case process has delta H equal to 60 and delta S equal to 0.2 in matching units. Where is its flip temperature?
- 12
- 300
- 0.003

Answer key

For grown-ups. Fold this page away before handing over the rest.

It can run alone · Negative change can run alone and even supply work.
H-TS · G equals H minus TS, balancing the two pulls.
False · Spontaneous sets direction only. Pace belongs to kinetics.
Equilibrium · Zero means forward and backward pulls balance.
T times delta S wins out · Melting gains disorder, so warming lets the entropy term win.
Always · Both teams pull forward, so no temperature can overturn it.
T times entropy beats heat cost · A large disorder gain can outscore the enthalpy cost, like ice melting in a warm room.
300 · Flip sits where terms tie: T equals delta H over delta S, 60 over 0.2 is 300.