Thermodynamics

Question 1

What are the 3 main types of thermodynamic systems?

Answer 1

1. **Open **- matter and energy flow in and out
2. **Closed **- only energy flows, not matter
3. Isolated - neither energy nor matter flow, essentially impossible and theoretical

Question 2

What are state variables?

Answer 2

AKA state functions

• thermodynamic variables such as P, V and T used to describe the equilibrium state of a system
• depend only on the current state of the system, not its history/how it reached its current state

Question 3

What is a quasistatic process?

Answer 3

• a thermodynamic process that happens “infinitely slowly”
• all reversible processes are quasistatic BUT some quasistatic processes are irreversible

Question 4

What are extensive vs. intensive parameters?

Answer 4

extensive - “depend on size” and can be summed

ie: mass, volume, charge, energy, entropy

intensive - “independent of size” and can not be summed

ie: temperature, pressure, concentration
ex: 1 L 1 Molar solution plus 1 L 2 Molar equals 2 L of 1.5 Molar solution … the intensive property of concentration is averaged rather than summed

Question 5

What is the 0th law of thermodynamics?

Answer 5

If two thermodynamic systems are both in equilibrium with a third, then all three are in equilibrium with each other.

Question 6

What is the first law of thermodynamics?

Answer 6

energy may be converted into different forms, but the total energy of a system remains constant

Question 7

What is the 2nd law of thermodynamics?

Answer 7

the entropy of an isolated system never decreases for spontaneous, irreversible processes and remains the same for reversible processes

• spontaneous processes move toward the most probable state, one with the most disorder
• originally stated simply that heat flows from hot to cold places (increasing their temperature and thus entropy) and not the opposite

Question 8

What is the 3rd law of thermodynamics?

Answer 8

the entropy of a pure crystalline substance at absolute zero is zero