Thermal Physics

Heat (Q) Energy transferred due to temperature difference; unit: joule (J)
Temperature (T) Measure of average kinetic energy of particles; unit: kelvin (K)
Absolute Zero 0 K, lowest possible temperature, minimum molecular motion
Thermal Expansion Increase in size of a material as temperature increases
Ideal Gas Particles have negligible volume and no intermolecular forces
Kinetic Theory Gas particles move randomly; pressure comes from collisions
1 Calorie Heat needed to raise 1 g of water by 1°C
Mechanical Equivalent of Heat 1 calorie = 4.186 joules; heat and work are equivalent
Specific Heat (c) Heat needed to raise 1 kg of substance by 1 K; Q = mcΔT
Heat Capacity (C) Heat needed to raise temperature of entire object by 1 K; C = mc
Calorimetry Measuring heat transfer using conservation of energy; heat lost = heat gained
Phase Change Change of state with no temperature change
Latent Heat (L) Heat required for phase change; Q = mL
Thermal Conductivity (k) Measure of how well a material conducts heat
Conduction Heat transfer by direct contact; Q/t = kAΔT/L
Convection Heat transfer by motion of fluids
Radiation Heat transfer by electromagnetic waves; no medium required
Work Done on a Gas W = ∫P dV; area under PV curve equals work done
First Law of Thermodynamics ΔU = Q − W
Internal Energy Total microscopic kinetic and potential energy of particles
Second Law of Thermodynamics Entropy of an isolated system always increases
Entropy (S) Measure of disorder; ΔS = Qrev / T
Ideal Gas Law PV = nRT; R = 8.31 J/mol·K
Isothermal Process Temperature constant
Adiabatic Process No heat transfer; Q = 0
Isobaric Process Pressure constant
Isochoric Process Volume constant; W = 0
Cyclic Process System returns to original state; ΔU = 0
Heat Engine Device that converts heat into work using hot and cold reservoirs
Thermal Efficiency e = Wout / Qin
Carnot Engine Efficiency e = 1 − Tc/Th
Blackbody Perfect absorber and emitter of radiation; depends only on temperature
Boltzmann Constant (kB) 1.38 × 10⁻²³ J/K; used for individual molecules
RMS Speed vrms = √(3kBT / m)
Relationship of R and kB R used for moles, kB for molecules; R = NAkB