Thermal Physics and Ideal Gases Flashcards

Absolute Zero

The lowest limit for temperature ($0\,\text{K}$ or $-273^\circ\text{C}$), defined as the temperature at which a substance has minimum internal energy, obeying $T(\text{K}) = \theta(^\circ\text{C}) + 273$.

Thermal Equilibrium

The state where objects in contact with each other are at the same temperature, resulting in no net heat flow between them because energy gained equals energy lost.

Solid (Particle Structure)

A state of matter where particles are in a regular arrangement fixed in rows and columns, vibrating about fixed positions and held by strong electrostatic forces of attraction.

Liquid (Particle Structure)

A state of matter where particles are randomly arranged to take the shape of their container, overlapping and flowing past each other with slightly weaker attractive forces.

Gas (Particle Structure)

A state of matter where particles are widely separated and very spread out, moving freely and randomly with negligible electrostatic forces.

Specific Heat Capacity ($c$)

The amount of energy required to raise the temperature of $1\,\text{kg}$ of a substance by $1\,\text{K}$, given by the equation $E = m \, c \, \Delta\theta$ (provided the substance is not changing phase).

Brownian Motion

The random movement of small visible particles suspended in a fluid (e.g. smoke particles in air) due to continuous collisions with much smaller, randomly moving atoms or molecules of the fluid.

Internal Energy

The sum of the randomly distributed kinetic and potential energies of atoms or molecules within a substance.

Maxwell-Boltzmann Distribution

A distribution showing the number of molecules at various molecular speeds, where the peak represents the most probable speed (the speed most particles have).

Assumptions of the Kinetic Model of a Gas

1. Large number of particles moving rapidly and randomly. 2. Particle volume is negligible compared to gas volume. 3. Collisions are perfectly elastic. 4. Collision duration is negligible compared to time between collisions. 5. Electrostatic forces are negligible except during collisions.

Ideal Gas

A gas that has internal energy only in the form of randomly distributed kinetic energy.

Mole

The amount of substance that contains as many particles as exactly $12.0\,\text{g}$ of carbon-12 (containing $6.02 \times 10^{23}$ particles).

Avogadro's Constant ($N_A$)

The number of particles per mole of any substance, equal to $N_A = 6.02 \times 10^{23}\,\text{mol}^{-1}$.

Molar Mass ($M_r$)

The mass of one mole of a substance, given by $M_r = \frac{m}{n}$ with units of $\text{g}\,\text{mol}^{-1}$.

Specific Latent Heat ($L$)

The energy required to change the state of $1\,\text{kg}$ of a substance with no change in temperature, given by $E = m \, L$.

Specific Latent Heat of Fusion ($L_f$)

The energy required per kilogram to change a substance between solid and liquid states without a change in temperature.

Specific Latent Heat of Vaporisation ($L_v$)

The energy required per kilogram to change a substance between liquid and gas states without a change in temperature.

Boyle's Law

At a constant temperature $T$, the pressure $P$ and volume $V$ of a fixed mass of gas are inversely proportional ($p V = \text{constant}$, $p_1 V_1 = p_2 V_2$).

Charles' Law

At a constant pressure $P$, the volume $V$ of a gas is directly proportional to its absolute temperature $T$ ($\frac{V}{T} = \text{constant}$, $V \propto T$).

Pressure-Temperature Law

At a constant volume $V$, the pressure $P$ of a gas is directly proportional