Thermal Physics - Key Terms (Lecture Notes)

Vocabulary flashcards covering key thermodynamics concepts: temperature scales and conversions, thermal expansion, phase changes, calorimetry, and related properties.

Relation between Celsius, Kelvin, and Fahrenheit scales

TC = TK − 273.15; TF = (9/5)·TC + 32; TC = (TF − 32)·5/9; TK = TC + 273.15.

Celsius and Fahrenheit equal reading

They read the same value at −40.0°.

Kelvin and Fahrenheit equal readings

They are numerically equal at 574.59° (K = °F numerically).

Kelvin and Celsius equal readings

Never (they never have the same numerical value at any temperature).

Healthy human body temperature

Approximately 37°C or 98.4°F.

Fusion

The process of transforming a solid into a liquid.

Melting point

Temperature at normal pressure (1 atm) at which a solid turns into liquid; ice melts at 0°C.

Vaporization

Transformation of a liquid to a gaseous state. Can occur by evaporation or boiling.

Evaporation

Liquid slowly changes to vapor from its exposed surface at any temperature.

Factors affecting evaporation

Flow of air, exposed surface area, nature of the liquid, air pressure, temperature, and dryness of air.

Boiling

Liquid rapidly converts to vapor upon heating, via application of heat.

Boiling point

Temperature at which vapor pressure equals atmospheric pressure; depends on external pressure.

Condensation (liquefaction)

Process of transforming a gaseous substance into a liquid.

Solidification

Process of transforming a liquid substance into a solid.

Latent heat of fusion (L_f)

Heat required to change 1 kg of a solid at its melting point to liquid, at the same temperature. Q = Lf m. Ice Lf ≈ 334000 J·kg⁻¹.

Latent heat of vaporization (L_v)

Heat required to change 1 kg of a liquid to gas at its boiling point, at constant temperature. Q = Lv m. Water Lv ≈ 334000 J·kg⁻¹.

Heat capacity (C)

Amount of heat required to raise the temperature of a body by 1 K. C = Q/(T₂ − T₁). Units: J·K⁻¹.

Specific heat (c or S)

Amount of heat required to raise the temperature of 1 kg of a substance by 1 K. S = Q/(m ΔT); units: J·kg⁻¹·K⁻¹.

Relation: heat capacity and specific heat

C = m × S; equivalently S = C/m; Therefore C = mS and S = C/m.

Calorimeter

A device used to measure the amount of heat involved in a chemical or physical process.

Principle of calorimetry

When two bodies at different temperatures are in contact, heat flows until thermal equilibrium; heat lost by the hotter body equals heat gained by the cooler body.

Regelation

Melting of a solid into liquid under pressure and re-solidification on release of pressure.