Branch of Physics, Chemistry and Engineering that focuses on converting energy, often in the form of heat and work.
Zeroth Law:
If two systems or objects are individually in thermal equilibrium with a third system or object, then they are also in thermal equilibrium with each other.
First Law (Law of Conservation of Energy):
Energy can neither be created nor destroyed; energy can only be transferred or converted from one form to another.
Second Law:
In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases. In other words, any spontaneous process increases the disorder of the universe.
Third Law:
The entropy of a system approaches a constant value as the temperature approaches absolute zero.
Total kinetic energy and potential energy of all the molecules in the system. It is the energy required to create the system.
Change in Internal Energy for a stationary thermodynamic process
ΔU = Q + W
Where, Q: Heat transferred to the system, W: Work done on the system
Change in Internal Energy for a stationary isobaric process
ΔU = Q − PΔV
An isobaric process is a thermodynamic process in which there is no change in pressure. Hence, Work done (W: Pressure-Volume Work) equals Pressure (P) times change in Volume (V).
Change in Internal Energy for a stationary isobaric process of Ideal Gases
ΔU = Q − nRΔT
Since, PV = nRT for ideal gases.
Change in Internal Energy for a stationary adiabatic process
ΔU = W
An adiabatic process is a thermodynamic process in which there is no heat transfer, hence Q = 0.
Change in Internal Energy for a stationary isochoric process
ΔU = Q
An isochoric process is a thermodynamic process in which there is no change in volume, i.e. there is no work done, hence W = 0.
Energy that comprises of system's internal energy, plus the amount of work required to establish its volume and pressure.
H = U + PV
Where, U: internal energy of the system, P: pressure, V: volume
Change in Enthalpy (ΔH)
ΔH = ΔU + Δ(PV)
Change in Enthalpy (ΔH) under constant Pressure
ΔH = Q
Where, Q: Heat transferred to the system
Since, Pressure (P) is constant, Δ(PV) = PΔV.
Change in Standard Molar Enthalpy (ΔH˚reaction)
ΔH˚reaction = ∑ (n p H˚products) - ∑ (n r H˚reactants)
| np | : number of moles in product in balanced chemical equation |
| H˚products | : standard enthalpy of products |
| nr | : number of moles in reactants in balanced chemical equation |
| H˚reactants | : standard enthalpy of reactants |
Measurement of molecular randomness or disorder.
Order of Entropy by State
Sgas > Ssolution > Sliquid > Ssolid
Change in Standard Molar Entropy (ΔS˚reaction)
ΔS˚reaction = ∑ (n p S˚products) - ∑ (n r S˚reactants)
| np | : number of moles in product in balanced chemical equation |
| S˚products | : standard entropy of products |
| nr | : number of moles in reactants in balanced chemical equation |
| S˚reactants | : standard entropy of reactants |