Physics -- Thermodynamics

Zeroth Law of Thermodynamics

objects are in thermal equilibrium when they are at the same temperature and therefore experience no net exchange of heat energy

Temperature

qualitative measure of how hot or how cold an object is; quantitatively, it is related to the average kinetic energy of the particles that make up the substance

System

portion of the universe we are interested in observing

Surroundings

include everything else in the universe that is not part of the system

Isolated systems

do not exchange matter or energy with the surroundings

Closed systems

exchange energy but not matter with the surroundings

Open systems

exchange both energy and matter with the surroundings

State functions

properties that depend only on the difference between the system's initial and final state, and not on the pathway taken between the initial and final state

Examples of state functions

Pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, and entropy

Process functions

describe the pathway from one equilibrium state to another

Examples of process functions

work and heat

First law of thermodynamics

law of conservation of energy: the total energy in the universe can never decrease nor increase

For a closed system, the total internal energy is _____ to the heat flow into the system minus the ____ done by the system

equal; work

Heat

the process of energy transfer between two objects at different temperatures that occurs until the two objects come into thermal equilibrium

Specific heat

the amount of energy necessary to raise one gram of a substance by 1 degree Celsius or by 1 kelvin

Four special types of thermodynamic systems in which a given variable is held constant

isothermal processes, adiabatic processes, isobaric processes, isovolumetric (isochoric) processes

Isothermal processes

temperature is constant and the change in internal energy is therefore 0

Adiabatic processes

no heat is exchanged

Isobaric processes

pressure is held constant

Isovolumetric (isochoric) processes

volume is held constant and the work done by or on the system is 0

Second law of thermodynamics

in a closed system (up to and including the entire universe), energy will spontaneously and irreversibly go from being localized to being spread out (dispersed)

Entropy

a measure of how spread out energy has become

Microstates and Entropy

Another way to understand entropy is the measure of molecular disorder, or the number of energy microstates available to a system at a given temperature

Natural process

in thermodynamics, a process which would occur as expected in nature

Of note, every natural process is ultimately (reversible/irreversible)

irreversible

Under highly controlled conditions, certain equilibrium processes such as phase changes can be treated as essentially (reversible/irreversible)

reversible

Specific heat formula

q = mcΔT

Equation for 1st thermodynamic law

∆U = q - W