Thermodynamics – Ideal Gas Law & Related Concepts

Vocabulary flashcards covering key terms and definitions from the lecture on state variables, pressure concepts, and the Ideal Gas Law.

State Variable

A measurable property (such as P, V, T, or N) that uniquely describes the condition of a system.

Pressure (P)

Force applied perpendicular to a unit area; measured in Pascals (Pa).

Pascal (Pa)

SI unit of pressure equal to one Newton per square meter (1 N / m²).

Atmospheric Pressure (atm)

Average air pressure at sea level, numerically 1 atm = 1.013 × 10⁵ Pa.

Gauge Pressure

Pressure measured relative to atmospheric pressure (does not include 1 atm baseline).

Absolute Pressure

Total pressure including atmospheric pressure; gauge pressure + 1 atm.

Volume (V)

The space occupied by a substance or system, typically measured in cubic meters (m³).

Temperature (T)

A measure of the average kinetic energy of particles; expressed in Kelvins (K) for gas laws.

Number of Particles (N)

Total count of molecules or atoms in a system.

Mole (mol)

Amount of substance containing Avogadro’s number of particles (6.022 × 10²³).

Avogadro’s Number (N_A)

6.022 × 10²³ particles per mole.

Equation of State

A mathematical relation connecting state variables of a system (e.g., PV = nRT).

Ideal Gas

Hypothetical gas whose molecules have no volume or intermolecular forces and obey PV = nRT exactly.

Ideal Gas Law (Macroscopic Form)

PV = nRT, relating pressure, volume, temperature, and moles for an ideal gas.

Ideal Gas Law (Microscopic Form)

PV = Nk_B T, relating pressure, volume, temperature, and number of molecules.

Boltzmann Constant (k_B)

Proportionality constant linking microscopic and macroscopic descriptions, k_B = 1.38 × 10⁻²³ J/K.

Universal Gas Constant (R)

R = 8.314 J/(K·mol); equal to NA kB.

Elastic Collision

A collision where kinetic energy is conserved; assumed between particles in an ideal gas.

Point Particle

Model assumption where gas molecules are treated as having negligible volume.

Thought Experiment

Hypothetical scenario used to explore theoretical ideas without physical experimentation.

Gauge vs Absolute Pressure

Gauge pressure excludes atmospheric pressure, while absolute pressure includes it.

Thermal Expansion of Gas

Increase in gas volume with rising temperature, described ideally by ΔV = βV₀ΔT for small changes.

Work Done by Gas (W)

For a quasi-static process at constant pressure, W = P ΔV.

Heat Transfer (Q = mcΔT)

Amount of heat added or removed equals mass × specific heat × temperature change.

First Law of Thermodynamics

ΔU = Q − W, linking change in internal energy to heat and work.