Physical Chemistry Terms

System

material of interest

Surroundings

everything outside the system

State

a set of conditions that fully define the properties of a system 

Equilibrium

state of the system shows no tendency to change

Thermodynamics

the understanding of how energy of a system relates to all the other measurables of a system

Relative Temperatures

reference points were set at the freezing and boiling points of water

Absolute Temperature

a temperature measured from absolute zero in kelvins

Laws

fundamental principles that describe the consistent and predictable behavior of matter, formed from numerous experimental observations and validated through repeated testing

Temperature

measure of how much kinetic energy the particles of a system have

Heat

energy transferred from one system to another due to temperature difference

Intensive Properties

do not depend on the amount

Extensive Properties

depend on the amount

Open System

exchange of mass or energy with the surroundings

Closed System

exchange of energy and no exchange of mass with the surroundings

Isolated System

no exchange of mass or energy with the surroundings

State Variables

variables that define the state

Equations of State

Equations defining the state

Compressibility Factor

a dimensionless quantity that measures how much a real gas deviates from an ideal gas

Expansion Coefficient of Gas

a measure of how its volume changes with temperature at constant pressure

Hard-Sphere Model

each gas particle is treated as a spherical particle having a specific radius within which no other gas particle can penetrate

Collision Diameter

the radius of the cylinder or the diameter of the particle

Collision Cross Section

in 3D, the cross section of this cylinder is a circle with the area pid²

Mean Free Path

average distance a particle travels between collisions

Average Collision Frequency

how many times a gas particle comes in contact with another gas particle each second

Effusion

the passage of gas particles through a barrier (like a small hole) into a different region where no particles (and usually no gas of any sort) existed previously

Diffusion

the passage of gas particles (or solute species, if in solution) from one part of the system to another with the total pressure constant in the system (that is, the transport isn’t due to pressure gradients)

Transport Property

describes the net movement of usually matter or energy through a nonuniform medium

Self-Diffusion

the random, independent movement of its molecules due to their internal kinetic energy, resulting in the mixing of the gas. It describes the motion of a gas's own molecules within a uniform gas phase, without the influence of external forces or concentration gradients between different substances

Mutual Diffusion

the net transport of all gas molecules in a mixture, driven by concentration and other gradients like temperature or pressure

Random Walk

as gas particles collide with others, their direction changes continuously but they ultimately end up moving from higher to lower concentration

Work

when an object moves some distance due to the application of force

Energy

the ability to do wor

Isothermal

the temperature remains constant for the product

Endothermic

heat enters system; q is positive

Exothermic

heat leaves system; q is negative

Internal Energy

the total energy of a system

Isolated System

does not allow for the passage of energy into or out of the system

Adiabatic 

if a system is insulated well enough, heat will not be able to get into the system or leave the system

State Function

any thermodynamic property whose value for the process is independent of the path

Isobaric Change

constant pressure change

Isochoric Change

constant volume change

Isenthalpic

the enthalpy of the gas does not change

Inversion Temperature

the temperature at which the Joule-Thomson coefficient goes from negative to positive

Vaporization

going from a liquid to a gas

Formation Reaction

any reaction making one mole of a product using, as reactants, the product’s constituent elements in their standard states