Thermodynamics and Kinetic Theory

Vocabulary practice flashcards covering the Ideal Gas Law, Kinetic Theory, Heat Transfer mechanisms, and the Laws of Thermodynamics.

Avogadro's Number ($N_A$)

The number of atoms or entities per mole, equal to $6.022 \times 10^{23}\,\text{mol}^{-1}$, named after Amedeo Avogadro.

Mole ($n$)

The SI base unit used to measure the amount of a substance, defined as the total number of particles ($N$) divided by Avogadro's number ($N_A$).

Ideal Gas Law

The equation of state relating absolute pressure ($P$), volume ($V$), number of moles ($n$), universal gas constant ($R = 8.31\,\text{J/(mol}\cdot\text{K)}$), and temperature in Kelvin ($T$), expressed as $PV = nRT$.

Boltzmann's Constant ($k$)

The proportionality constant defined as $k = \frac{R}{N_A}$, equal to $1.38 \times 10^{-23}\,\text{J/K}$, which allows the ideal gas law to be written as $PV = NkT$.

Alveoli

Tiny air sacs in the lungs separated from capillary blood by a thin respiratory membrane, where oxygen enters the blood.

Maxwell-Boltzmann Distribution

The molecular speed distribution calculated by physicist James Clark Maxwell, describing the distribution of speeds in a large collection of molecules at a constant temperature.

Temperature (Kinetic Interpretation)

A property directly proportional to the average translational kinetic energy per particle of an ideal gas ($\overline{KE} = \frac{3}{2}kT$), independent of pressure and volume.

Internal Energy of a Monatomic Ideal Gas ($U$)

The sum of the translational kinetic energies of all $N$ atoms in the gas, represented as $U = \frac{3}{2}NkT = \frac{3}{2}nRT$.

First Law of Thermodynamics

The energy conservation principle applied to thermal systems, written as $\Delta U = Q - W$, where $\Delta U$ is the change in internal energy, $Q$ is the net heat added, and $W$ is the work done by the system.

Isobaric Process

A thermodynamic process that occurs at constant pressure, where the work done by expanding gas is $W = P\Delta V = P(V_f - V_i)$.

Isovolumetric Process (Isochoric Process)

A thermodynamic process that occurs at constant volume, in which no work is done ($W = 0\,\text{J}$) and all transferred heat changes the internal energy ($\Delta U = Q$).

Adiabatic Process

A thermodynamic process occurring without heat transfer ($Q = 0$), where the change in internal energy directly corresponds to work done ($\Delta U = -W$).

Work on a Pressure-Volume Graph

The work done during a thermodynamic expansion or compression, given by the area under the curve on a $P\text{-}V$ diagram.

Thermal Conductivity ($k$)

A material property indicating the ability to conduct heat, expressed in units of $\text{J}/(\text{s}\cdot\text{m}\cdot^\circ\text{C})$ or $\text{W}/(\text{m}\cdot^\circ\text{C})$.

Heat Conduction Rate Equation

The relation $Q = \frac{k A \Delta T \, t}{L}$, calculating heat ($Q$) conducted through a material of cross-sectional area $A$, length $L$, and temperature difference $\Delta T$ over time $t$.

Molar Specific Heat Capacity at Constant Volume ($C_v$)

The amount of heat per mole required to raise the temperature of a gas by one degree at constant volume, equal to $\frac{3}{2}R$ for a monatomic ideal gas.

Molar Specific Heat Capacity at Constant Pressure ($C_p$)

The amount of heat per mole required to raise the temperature of a gas by one degree at constant pressure, equal to $\frac{5}{2}R$ for a monatomic ideal gas.

Zeroth Law of Thermodynamics

The principle stating that if two systems are each in thermal equilibrium with a third system, they are also in thermal equilibrium with each other.

Second Law of Thermodynamics

The principle stating that heat flows spontaneously from hot to cold, and can only flow from cold to hot if external work is done on the system.

Entropy

A measure of the dispersal or disorder of energy and molecular configurations within a system.

Irreversible Process

A process that cannot naturally run backward without external work, resulting in an increase in entropy and an unavoidable loss of usable work.

Convection

The transfer of heat caused by the bulk movement of a fluid.

Radiation

The transfer of thermal energy through electromagnetic waves without requiring a physical medium.

Isothermal Process

A thermodynamic process occurring at constant temperature ($\Delta T = 0$), where internal energy remains unchanged ($\Delta U = 0$) and work is given by $W = nRT \ln\left(\frac{V_f}{V_i}\right) = Q$.

Formula for Moles from Mass and Molar Mass

$n = \frac{m}{M}$, where $n$ is the amount in moles, $m$ is the mass of the sample, and $M$ is the molar mass.

Formula for Number of Particles from Moles

$N = n N<em>A$, where $N$ is the total number of particles, $n$ is the amount in moles, and $N</em>A$ is Avogadro's number ($6.022 \times 10^{23}\,\text{mol}^{-1}$).

Formula for Number of Particles from Sample Mass

$N = \left(\frac{m}{M}\right) N<em>A$, where total particles ($N$) is calculated by dividing sample mass ($m$) by molar mass ($M$) to find moles, and then multiplying by Avogadro's number ($N</em>A$).

Formula for Mass of a Single Particle ($m_0$)

$m<em>0 = \frac{M}{N</em>A}$, calculated by dividing the molar mass ($M$) of the substance by Avogadro's number ($N_A$).

Entropy Increases ($\Delta S > 0$)

Occurs when energy becomes more dispersed, molecules spread out, or a system transitions to a more disordered state (e.g., solid to liquid, liquid to gas, or heating a substance).

Entropy Decreases ($\Delta S < 0$)

Occurs when energy becomes more localized, molecules become more ordered, or a system transitions to a more structured state (e.g., gas to liquid, liquid to solid, or cooling a substance).

System Entropy Increase ($+\Delta S_{\text{system}}$)

Happens when a system expands, increases in temperature, absorbs heat, or undergoes a phase change from solid to liquid or liquid to gas.

System Entropy Decrease ($-\Delta S_{\text{system}}$)

Happens when a system is compressed, decreases in temperature, releases heat to the surroundings, or undergoes a phase change from gas to liquid or liquid to solid.

Surroundings Entropy Increase ($+\Delta S_{\text{surroundings}}$)

Occurs when a system releases heat into its environment ($Q_{\text{system}} < 0$), causing the thermal energy and motion of the surrounding molecules to spread out and increase.

Surroundings Entropy Decrease ($-\Delta S_{\text{surroundings}}$)

Occurs when a system absorbs heat from its environment ($Q_{\text{system}} > 0$), drawing thermal energy away from the surroundings and reducing their molecular motion.

Second Law of Thermodynamics (Entropy Criterion)

States that for any spontaneous natural process, the total entropy of the universe must always increase or remain constant for a reversible process ($\Delta S_{\text{universe}} \ge 0$).

Universe Entropy Change ($\Delta S_{\text{universe}}$)

The sum of the entropy change of the system and its surroundings ($\Delta S<em>{\text{system}} + \Delta S</em>{\text{surroundings}}$), which can never decrease in a real-world, spontaneous process.

Reversible Process Entropy Change ($\Delta S_{\text{universe}} = 0$)

An idealized, frictionless, quasi-static process where the total entropy of the universe remains constant (entropy gained by one part is exactly lost by another).

Irreversible Process Entropy Change ($\Delta S_{\text{universe}} > 0$)

Any real, spontaneous process (like heat flowing naturally from hot to cold, or friction) where the total entropy of the universe strictly increases.