Energy Transfer by Heat: Vocabulary (Specific Heat & Latent Heat)

Vocabulary flashcards covering heat, temperature, specific heat, latent heat, phase changes, and related thermodynamics concepts from the lecture notes.

Heat

Energy transferred between objects due to a temperature difference; flows from hotter to colder substances; heat is not a property contained in matter.

Temperature

A measure of the average kinetic energy of particles in a substance; not the energy itself.

Specific Heat Capacity (c)

Energy required to raise the temperature of 1 kg of a substance by 1 K; units: J/(kg·K); for constant c, Q = m c ΔT.

Q = m c ΔT

Heat transferred during a temperature change for constant specific heat.

dQ = m c dT

Differential form of heat transfer; used when c may vary with temperature.

Temperature-Dependent Specific Heat

Specific heat that changes with temperature; energy is computed with Q = ∫ m c(T) dT.

Latent Heat (L)

Heat required for a phase change per unit mass; sign of Q depends on the direction of the phase change: Q = ± m L.

Latent Heat of Fusion (L_f)

Heat required to melt or freeze a substance per unit mass (solid ↔ liquid); example: ice L_f ≈ 334 kJ/kg.

Latent Heat of Vaporization (L_v)

Heat required to vaporize or condense a substance per unit mass (liquid ↔ gas); example: water L_v ≈ 2256 kJ/kg.

Phase Change

Transition between solid, liquid, and gas; during phase change, temperature remains constant while internal energy changes due to bond breaking/forming.

Phase Change Temperature

The temperature at which a phase change occurs (melting point, boiling point); remains constant during the phase change.

Heat Transfer by Work (W)

Energy transferred due to a volume change; W = ∫ P dV; at constant pressure, W = P ΔV.

Ideal Gas Law (PV = nRT)

Relationship among pressure, volume, and temperature for an ideal gas; R = 8.314 J/(K·mol).

Pressure-Volume Work (PΔV)

Work done during a volume change at constant pressure; W = P ΔV.

SI Unit of Heat

The joule (J); larger quantities are often expressed in kilojoules (kJ).

Sign Convention for Latent Heat

Q is positive for melting/boiling (heat into system) and negative for freezing/condensation (heat out of system).

Boiling Point of Water

100°C (373.15 K) at 1 atm; temperature at which liquid water boils.

Energy During Heating Curve

Temperature rises with heat input until phase-change temperature is reached; after that, added heat goes into changing phase rather than increasing temperature.

Energy Variation with Material

Different materials require different amounts of heat to raise their temperature due to particle structure and mass.

Latent Heats (Ice-Water)

Lf ≈ 334 kJ/kg (fusion); Lv ≈ 2256 kJ/kg (vaporization) for water, used in phase-change calculations.

Non-constant Specific Heat Case

When c depends on T, use Q = ∫ m c(T) dT rather than Q = m c ΔT.

R and Units

R is the universal gas constant, 8.314 J/(K·mol), used in PV = nRT.