Thermodynamics Midterm 1 theory

equilibrium state

one in which all the bulk physical properties of the system are uniform throughout the system and do not change with time

state functions

internal energy, entropy, enthalpy

adiabatic

the volume changes, but the pressure does not

diathermal

both the volume and the pressure changes, there is a thermal interaction

thermal contact

two systems in contact via a diathermal wall

thermal equilibrium

if two thermodynamic systems are put into thermal contact, after a time no further changes in the pressures an volumes will occur.

zeroth law of thermodynamics

if each of two systems is in thermal equilibrium with a third, they are in thermal equilibrium with one another

temperature

the temperature of a system is a property that determines whether or not that system is in thermal wquilibrium with other systems. Systems in thermal equilibrium with one another have the same temperature T

conditions for thermodynamic equilibrium

mechanical, chemical, diffusive and thermal equilibrium

general equation of state

f(P, V, T) = 0

equation of state for ideal gas

PV = nRT

process

the mechanism of bringing about changes in a system such that it changes from one equilibrium state to another. These initial and final equilibrium states are called the end points of the process

reversible processes

in any change, the system must be capable of being returned to its original state and leaving the surroundings unchanged too

quasiatic process

a process that can be thought of a succession of equilibrium states. Reversible processes are quasiatic processes where no dissipative forces such as friction are present

thermal expansion

solids and liquids generally expand when their temperature increases

dissipative work

work done by non-conservative forces that cannot be reversed in a system

intensive variable

the variable is size independent

extensive variable

the variable is size dependent

first law of thermodynamics

if a thermally isolated system is brought from one equilibrium state to another, the work necessary to achieve this change is independent of the process used

deltaU=W+Q

heat

the nnmechanical exchange of energy between the system and the surroundings because of their temperature difference

enthalpy

the total energy in a thermodynamic system
H=U+PV

latent heat

the amount of heat energy required to change the phase of a substance without changing its temperature

equipartition theorem

in thermodynamic equilibrium at temperature T, each independent quadratic degree of freedom contributes ½ k_B*T to the mean energy of a molecule

adiabat

the curve that describes an adiabatic process

isenthalpic process

a process in which there is no change in the enthalpy

steady flow

the flow of a fluid at a constant rate through a device so that some of the internal energy of the fluid transforms into mechanical work

Carnot’s theorem

no engine operating between two reservoirs can be more efficient than a carnot engine operating between those two reservoirs

heat engine

an engine that uses the flow of heat from a higher temperature reservoir to a lower temperature reservoir to do work

Kelvin-Planck statement (2nd law)

it is impossible to construct a device that, operating in a cycle, will produce no other effect other then the extraction of heat from a single body at a uniform temperature and produce an equivalent amount of work

Clausius statement (2nd law)

it is impossible to construct a device that, operating in a cycle, produces no other effect than the transfer heat from a colder body to a hotter body