Lecture 3 Flashcards
is a
substance that has a fixed
chemical composition
throughout.
E.g. water, nitrogen,
helium, and carbon
dioxide
pure substance
does not
have to be of a single chemical
element or compound,
however. A mixture of various
chemical elements or
compounds also qualifies as a
pure substance as long as the
mixture is homogeneous.
pure substance
Solid molecules are
arranged in a _________ which
is an ordered array of
points describing the
arrangement crystal-
forming particles.
lattice
begins when solid molecules
reach a point where they can escape these strong
intermolecular forces upon reaching sufficiently high
temperatures.
“melting” process
State 1 is __________
state since it is not ready to
vaporize.
a compressed liquid
a
liquid that is about to vaporize
saturated liquid
A vapor that is
about to condense
is called a __________
saturated vapor
A substance at states between 2 and 4 is referred to as a
_____________ since the liquid and
vapor phases coexist in equilibrium at these states.
saturated liquid–vapor mixture
A vapor that is not about to condense is called a __________
superheated vapor
the temperature at
which a pure substance
changes phase at a given
pressure
saturation temperature,
Tsat
the pressure at which a
pure substance changes phase at a given temperature
saturation pressure, Psat
the amount of energy absorbed or
released during a phase change process
Latent Heat
the amount of energy absorbed
during melting equal to the amount of energy released
during freezing
Latent Heat of Fusion
the amount of energy
absorbed during vaporization equal to the energy
released during condensation
Latent Heat of Vaporization
A plot of Psat versus
Tsat is called a _______. A curve of this
kind is characteristic of all pure substances.
liquid–
vapor saturation
curve.
the point at which the saturated liquid
and saturated vapor states are identical
Critical Point
The temperature, pressure, and specific volume of a
substance at the critical point are called, respectively, the _______, __________ and __________.
critical temperature Tcr, critical pressure Pcr, and critical
specific volume vcr.
At ____________ there is not
a distinct phase-change
process. Instead, the specific
volume of the substance
continually increases, and at
all times there is only one
phase present.
pressures above the
critical pressure
there is no line that
separates the compressed liquid
region and the superheated
vapor region.
Above the critical state
It is customary to refer to the substance as ________ at temperatures above the critical temperature and as ________ at temperatures below the
critical temperature.
superheated
vapor; compressed liquid
a line connecting the saturated
liquid states
Saturated Liquid Line
a line connecting the saturated
vapor states
Saturated Vapor Line
All the compressed liquid states are located in the region
to the left of the saturated liquid line, called the _________
compressed liquid region
All the superheated vapor states are located to the right
of the saturated vapor line, called the __________
superheated
vapor region
All the states that involve both phases in equilibrium are
located under the dome, called _________
the saturated liquid–
vapor mixture region, or the wet region
The P-T diagram - This is also called the _________
Phase Diagram
The _________ separates the solid and
vapor regions;
sublimation line
The _________ separates the liquid and
vapor regions
vaporization line
the _________ line separates the
solid and liquid regions.
melting or fusion
The aforementioned three lines meet at the ________,
where all three phases coexist in equilibrium
triple point
A thermodynamic
property designed simplify our
reference to the combined
values of Pv and u terms.
Enthalpy, h
The quantity hfg is called the _________. It represents the amount of
energy needed to vaporize a unit mass of saturated liquid
at a given temperature or pressure. It decreases as the
temperature or pressure increases and becomes zero at
the critical point.
enthalpy of vaporization (or
latent heat of vaporization)
the ratio of the mass of vapor to the total
mass of the mixture
Quality, x
A saturated mixture can be treated as a combination of
two subsystems:
saturated liquid; saturated vapor
Any equation that relates the pressure, temperature, and
specific volume of a substance is called an _________
equation of state
The simplest and best known equation of state for
substances in the gas phase is the _________
ideal gas equation of
state
_________ is called the gas
constant
constant of proportionality R
the ideal-gas equation
of state, or simply the ideal-gas relation, and a gas that
obeys this relation is called an
ideal gas
defined as the mass of
one mole of a substance in grams, or the mass of one
kmol in kilograms, or the mass of one lbmol in lbm.
M, the molar mass of the gas
An _________ is an imaginary substance that obeys the
relation Pv = RT
ideal gas
