Cambridge A Level Physics 9702: Thermal Physics & Thermodynamics Master Vocabulary

Comprehensive vocabulary flashcards focusing on definitions, laws, and key parameters for Cambridge International A Level Physics 9702 (Temperature, Ideal Gases, Thermodynamics).

Temperature

A measure related to the average kinetic energy of the particles in a substance.

Thermal Equilibrium

A state in which two objects in thermal contact have no net transfer of thermal energy between them and are at the same temperature.

Zeroth Law of Thermodynamics

The law stating that if object A is in thermal equilibrium with B, and B is in thermal equilibrium with C, then A and C are also in thermal equilibrium.

Absolute Zero

The lowest possible thermodynamic temperature, equal to $0\,\text{K}$ or approximately $-273.15\,^\circ\text{C}$, where particle kinetic energy reaches its theoretical minimum.

Thermometric Property

A physical quantity (such as volume of a liquid, electrical resistance, or pressure) that changes predictably with temperature.

Lower Fixed Point

The melting point of pure ice at standard atmospheric pressure, defined as $0\,^\circ\text{C}$.

Upper Fixed Point

The boiling point of pure water at standard atmospheric pressure, defined as $100\,^\circ\text{C}$.

Sensitivity (Thermometer)

The change in the thermometric property per unit change in temperature, given by $S = \frac{\Delta X}{\Delta T}$.

Range (Thermometer)

The interval of temperatures over which a thermometer can provide useful measurements.

Resolution

The smallest change in temperature that can be detected or displayed by a measuring instrument.

Response Time

The time required for a thermometer to reach thermal equilibrium and approach the actual temperature of the object being measured.

Internal Energy

The total microscopic energy associated with the particles of a system, consisting of random kinetic energy and potential energy.

Specific Heat Capacity

The energy required to raise the temperature of unit mass of a substance by one kelvin, expressed as $c = \frac{Q}{m\Delta T}$ with unit $\text{J}\,\text{kg}^{-1}\,\text{K}^{-1}$.

Ideal Gas

A theoretical model of a gas whose point-mass molecules move in continuous random motion, occupy negligible volume, experience no intermolecular forces except during elastic collisions, and obey Newton's laws.

Boyle's Law

The rule stating that for a fixed mass of gas at constant temperature, pressure is inversely proportional to volume ($P \propto \frac{1}{V}$).

Charles' Law

The rule stating that for a fixed mass of gas at constant pressure, volume is directly proportional to absolute temperature ($V \propto T$).

Pressure Law

The rule stating that for a fixed mass of gas at constant volume, pressure is directly proportional to absolute temperature ($P \propto T$).

Ideal Gas Equation

The equation of state connecting pressure, volume, amount, and absolute temperature: $PV = nRT$ (macroscopic) or $PV = NkT$ (microscopic).

Mean Square Speed

The average value of the squared speeds of all molecules in a gas sample, denoted as \langle c^2 \rangle.

Root-Mean-Square Speed ($c_{\text{rms}}$)

The square root of the mean square speed of gas molecules, given by $c_{\text{rms}} = \sqrt{\langle c^2 \rangle} = \sqrt{\frac{3RT}{M}}$.

Boltzmann Constant ($k$)

A physical constant representing the gas constant per molecule, equal to $k = \frac{R}{N_A} \approx 1.38 \times 10^{-23}\,\text{J}\,\text{K}^{-1}$.

Brownian Motion

The random motion of relatively large particles suspended in a fluid caused by uneven bombardment from rapidly moving molecules, providing evidence for microscopic particle motion.

First Law of Thermodynamics

The law of energy conservation stating that the increase in internal energy equals the thermal energy transferred to the system plus the work done on it ($\Delta U = Q + W$).

Work Done by a Gas

The mechanical energy transferred when a gas expands against external pressure, calculated as $W = P\Delta V$ at constant pressure or as the area under a $P - V$ curve.

Second Law of Thermodynamics

The law stating that thermal energy naturally transfers from higher to lower temperature regions and cannot spontaneously transfer in reverse without external work.

Heat Engine

A cyclic device that absorbs thermal energy from a hot reservoir, converts a portion of it into mechanical work, and rejects the remainder to a cold reservoir.

Carnot Engine

An ideal reversible heat engine operating between two temperatures that achieves maximum theoretical efficiency, given by $\eta = 1 - \frac{T_C}{T_H}$.

Entropy

A measure associated with the dispersal of energy and the number of possible microscopic arrangements of a system, where $\Delta S = \frac{Q_{\text{rev}}}{T}$.

Specific Latent Heat

The energy required to change the state of unit mass of a substance without changing its temperature ($Q = mL$), with unit $\text{J}\,\text{kg}^{-1}$.

Isothermal Process

A thermodynamic process occurring at constant temperature ($T = \text{constant}$, $\Delta U = 0$ for an ideal gas).

Adiabatic Process

A thermodynamic process in which no thermal energy enters or leaves the system ($Q = 0$, $\Delta U = -W$).

Isobaric Process

A thermodynamic process occurring at constant pressure ($P = \text{constant}$, $W = P\Delta V$).

Isochoric Process

A thermodynamic process occurring at constant volume ($V = \text{constant}$), resulting in zero work done ($W = 0$).

State Function

A thermodynamic quantity (such as pressure, volume, temperature, or internal energy) whose value depends only on the current state of the system, not on the path taken to reach it.