Thermodynamics — Formula Sheet

W = PΔV = P(V₂ - V₁)

1 cal = 4.18 J

Isothermal: T = constant, ΔT = 0

Adiabatic: ΔQ = 0, so ΔU = -ΔW

Isobaric: P = constant, W = PΔV

Isochoric: ΔV = 0, so ΔW = 0, and ΔQ = ΔU

Cyclic Process: ΔU = 0, so ΔQ = ΔW

ΔU = ΔQ - ΔW

Uᵢ - U_f = -W (adiabatic)

U = KE_molecules + PE_molecules

Unit of heat

1 calorie = 4.18 Joules; 1 kcal = 1000 cal = 4180 J.

Isothermal Process

Temperature is constant (ΔT = 0). Occurs in perfectly conducting cylinders. ΔQ, ΔU, and ΔW are all finite. For an ideal gas, ΔU = 0, so ΔQ = ΔW.

Adiabatic Process

No heat exchange (ΔQ = 0). Occurs in perfectly insulating cylinders. From First Law: ΔU = −ΔW. If gas is compressed, work is done ON the gas, ΔU increases (gas heats up). If gas exp

Isobaric Process

Pressure is constant (ΔP = 0). Example: Heating water under atmospheric pressure. Work done W = PΔV is non-zero.

Adiabatic

No heat exchange (ΔQ = 0), perfectly insulated system

Triple point

All three phases coexist; for water, T = 273.16 K and P = 611.73 Pa

Five major processes

(1) Isothermal: Temperature is constant (T = const).