PHY 102 – Thermal Physics Vocabulary

A set of vocabulary flashcards summarizing fundamental terms and formulas from the PHY 102 lecture on Thermal Physics, covering temperature, heat, phase change, heat transfer mechanisms, kinetic theory, and thermodynamic laws.

Zeroth Law of Thermodynamics

If two bodies are each in thermal equilibrium with a third body, they are in thermal equilibrium with each other.

Thermal Equilibrium

State in which no net heat flow occurs between objects because they are at the same temperature.

Temperature

Property that determines the direction of heat flow between two objects in thermal contact.

Thermometer

Device that measures temperature by exploiting a temperature-dependent physical property (e.g., volume, pressure, resistance).

Celsius Scale

Temperature scale with ice point at 0 °C and steam point at 100 °C.

Fahrenheit Scale

Temperature scale with ice point at 32 °F and steam point at 212 °F.

Kelvin Scale

Absolute temperature scale with true zero at 0 K; 0 K = −273.15 °C.

Absolute Zero

Temperature at which the internal energy of an ideal gas is minimal; 0 K.

Coefficient of Linear Expansion (α)

Fractional change in length per degree change in temperature; ∆L = αL₀∆T.

Coefficient of Volume Expansion (β)

Fractional change in volume per degree change in temperature; β = 3α for isotropic solids.

Specific Heat Capacity (c)

Heat required to raise the temperature of unit mass of a substance by 1 °C (or 1 K).

Quantity of Heat (Q)

Energy transferred as heat; Q = mc∆T for a temperature change in a single phase.

Calorimetry

Measurement of heat transfer using the principle heat lost = heat gained.

Latent Heat (L)

Energy per unit mass required for a phase change at constant temperature.

Latent Heat of Fusion (L_f)

Energy needed to change unit mass from solid to liquid at constant temperature.

Latent Heat of Vaporization (L_v)

Energy needed to change unit mass from liquid to vapor at constant temperature; larger than L_f.

Newton’s Law of Cooling

Rate of heat loss of a body is proportional to the temperature difference between body and surroundings: dQ/dt = −k(T−T₀).

Conduction

Heat transfer through a material without bulk motion of the material itself.

Thermal Conductivity (k)

Material constant indicating ability to conduct heat; high k → good conductor.

Conduction Equation

dQ/dt = −kA( T₁−T₂ )/ℓ for steady conduction through a slab.

Convection

Heat transfer by bulk movement of a fluid; dQ/dt = hA( T−T₀ ).

Convection Coefficient (h)

Empirical constant characterizing convective heat transfer efficiency.

Radiation

Energy transfer by electromagnetic waves; requires no material medium.

Stefan–Boltzmann Constant (σ)

Universal constant in radiation law; σ = 5.67×10⁻⁸ W m⁻² K⁻⁴.

Stefan–Boltzmann Law

Radiant power: dQ/dt = εσA T⁴ ; net loss = εσA( T₁⁴−T₂⁴ ).

Emissivity (ε)

Dimensionless number (0–1) describing how effectively a surface emits or absorbs radiation.

Kinetic Theory of Gases

Model treating gas molecules as small particles in random, elastic motion obeying classical mechanics.

Root-Mean-Square Speed (v_rms)

√(3kT/m) or √(3RT/M); statistical measure of molecular speed in a gas.

Ideal Gas Law

PV = NkT = nRT; relates pressure, volume, and temperature for an ideal gas.

Internal Energy (U)

Total microscopic kinetic and potential energy of the molecules of a system.

First Law of Thermodynamics

∆Q = ∆U + ∆W; energy conservation relating heat, internal energy change, and work.

Thermodynamic Work (W)

Energy transfer by macroscopic forces; for gases, W = P∆V.

Isothermal Process

Thermodynamic process at constant temperature (∆U = 0); ∆Q = W.

Adiabatic Process

Process with no heat exchange (∆Q = 0); ∆U = −W.

Isochoric (Isovolumic) Process

Process at constant volume (∆V = 0); W = 0, so ∆Q = ∆U.

Isobaric Process

Thermodynamic process at constant pressure.

Second Law of Thermodynamics

Heat flows spontaneously from hot to cold bodies; no cyclic process converts heat entirely into work without other effects.

System

Part of the universe chosen for analysis; may be open, closed, or isolated.

Closed System

System where mass stays constant but energy may cross boundaries.

Isolated System

Closed system with no exchange of energy or matter with surroundings.

Heat

Energy transfer due solely to temperature difference between system and surroundings.

Work

Energy transfer not caused by a temperature difference, often associated with macroscopic forces.