Thermodynamics (Physics Chapter 3)

Question 1

What is the zeroth law of thermodynamics?

Answer 1

The zeroth law of thermodynamics states that when two objects are in thermal equilibrium with a third object, they are in thermal equilibrium with each other.

• By extension, no heat flows between two objects in thermal equilibrium.

Question 2

What physical properties of matter change when the matter gets hotter or colder?

Answer 2

Length, volume, solubility, and conductivity.

Question 3

What is thermal expansion?

Answer 3

Thermal expansion describes how a substance changes in lenght or volume as a function of the change in temperature.

• Linear expansion equation (mnemonic alot):

delta (L) = (alpha) x (L) x delta (T)

• Volumetric expansion equation is the same as linear, except substitute Volume (V) for length (L).

Question 4

What is the difference between an isolated sytem and a closed system?

Answer 4

A closed system can exchange energy (heat) but not matter with the surroundings. An isolated system cannot exchange energy or matter with their surroundings.

Question 5

What is the difference between state functions and process functions?

Answer 5

• State functions are pathway independent and are scalar quantities.
  
  • Ex: Gibbs free energy, entropy, enthalpy, density, volume, temprerature, pressure, internal energy
• Process functions are pathway dependent and are vector quantities.
  
  • Ex: Heat and work

Question 6

What is the first law of thermodynamics?

Answer 6

The first law of thermodynamics states that the change in the total internal energy(U) of a system is equal to the amount of energy transferred in the form of heat(Q) to th system, minus the amount of energy transferred from the system in the form of work.

Basically: delta (U) = Q - W

Question 7

What is the second law of thermodynamics?

Answer 7

The second law of thermodynamics states that objects in thermal contact and not in thermal equilibrium will exchange heat energy, such that the object with a higher temperature will transfer heat (energy) to the object with a lower termperture until both objects have the same temperature at thermal equilibrium.

Question 8

What is heat (Q)?

Answer 8

Heat is the process in which a quantity of energy is transferred between two objects as a result of a difference in temperature.

Question 9

What is the SI unit for heat and its conversion into calories?

Answer 9

The SI unit for heat is the Joule (J) and the conversion factors are:

1 Cal = 1000 cal = 4184 J

Question 10

What is sublimation and deposition?

Answer 10

Sublimation is the phase change of a substance from a solid into a gas. Deposition is the reverse process of a substance undergoing a phase change from a gas to a solid.

Question 11

What is fusion and vaporization?

Answer 11

Fusion(melting) is when a substance undergoes a phase change from a solid to a liquid. Vaporization(boiling, evaporization) is when a substance undergoes a phase change from a liquid to a gas.

Question 12

What is an adiabatic process and how does it relate to the 1st law of thermodynamics?

Answer 12

• An adiabatic process is when there is no heat exchange between the system and its surroundings (no heat gain or loss by the system; Q = 0).
• Since Q = 0, then delta (u) = -W

Question 13

How does an isothermal process relate to the 1st law of thermodynamics?

Answer 13

• If the process is isothermal, the internal energy of the system does not increase or decrease [delta(U) = 0].
• Since delta(U) = 0 then Q = W.

Question 14

How does an isovolumetric (isochoric) process relate to the 1st law of thermodynamics?

Answer 14

• An isochoric process means that W = 0 because W = P x delta(V).
• Since W = 0 then that must mean delta(U) = Q.

Question 15

How do you calculate the change in entropy of a system without using gibbs free energy equation?

Answer 15

delta(s) = Q_rev / T

• Must be a reversible process, if not it cannot be calculated