Lecture 3

Question 1

is a
substance that has a fixed
chemical composition
throughout.
E.g. water, nitrogen,
helium, and carbon
dioxide

Answer 1

pure substance

Question 2

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.

Answer 2

pure substance

Question 3

Solid molecules are
arranged in a _________ which
is an ordered array of
points describing the
arrangement crystal-
forming particles.

Answer 3

lattice

Question 4

begins when solid molecules
reach a point where they can escape these strong
intermolecular forces upon reaching sufficiently high
temperatures.

Answer 4

“melting” process

Question 5

State 1 is __________
state since it is not ready to
vaporize.

Answer 5

a compressed liquid

Question 6

a
liquid that is about to vaporize

Answer 6

saturated liquid

Question 7

A vapor that is
about to condense
is called a __________

Answer 7

saturated vapor

Question 8

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.

Answer 8

saturated liquid–vapor mixture

Question 9

A vapor that is not about to condense is called a __________

Answer 9

superheated vapor

Question 10

the temperature at
which a pure substance
changes phase at a given
pressure

Answer 10

saturation temperature,
Tsat

Question 11

the pressure at which a
pure substance changes phase at a given temperature

Answer 11

saturation pressure, Psat

Question 12

the amount of energy absorbed or
released during a phase change process

Answer 12

Latent Heat

Question 13

the amount of energy absorbed
during melting equal to the amount of energy released
during freezing

Answer 13

Latent Heat of Fusion

Question 14

the amount of energy
absorbed during vaporization equal to the energy
released during condensation

Answer 14

Latent Heat of Vaporization

Question 15

A plot of Psat versus
Tsat is called a _______. A curve of this
kind is characteristic of all pure substances.

Answer 15

liquid–
vapor saturation
curve.

Question 16

the point at which the saturated liquid
and saturated vapor states are identical

Answer 16

Critical Point

Question 17

The temperature, pressure, and specific volume of a
substance at the critical point are called, respectively, the _______, __________ and __________.

Answer 17

critical temperature Tcr, critical pressure Pcr, and critical
specific volume vcr.

Question 18

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.

Answer 18

pressures above the
critical pressure

Question 19

there is no line that
separates the compressed liquid
region and the superheated
vapor region.

Answer 19

Above the critical state

Question 20

It is customary to refer to the substance as ________ at temperatures above the critical temperature and as ________ at temperatures below the
critical temperature.

Answer 20

superheated
vapor; compressed liquid

Question 21

a line connecting the saturated
liquid states

Answer 21

Saturated Liquid Line

Question 22

a line connecting the saturated
vapor states

Answer 22

Saturated Vapor Line

Question 23

All the compressed liquid states are located in the region
to the left of the saturated liquid line, called the _________

Answer 23

compressed liquid region

Question 24

All the superheated vapor states are located to the right
of the saturated vapor line, called the __________

Answer 24

superheated
vapor region

Question 25

All the states that involve both phases in equilibrium are located under the dome, called _________

Answer 25

the saturated liquid– vapor mixture region, or the wet region

Question 26

The P-T diagram - This is also called the _________

Answer 26

Phase Diagram

Question 27

The _________ separates the solid and vapor regions;

Answer 27

sublimation line

Question 28

The _________ separates the liquid and vapor regions

Answer 28

vaporization line

Question 29

the _________ line separates the solid and liquid regions.

Answer 29

melting or fusion

Question 30

The aforementioned three lines meet at the ________, where all three phases coexist in equilibrium

Answer 30

triple point

Question 31

A thermodynamic property designed simplify our reference to the combined values of Pv and u terms.

Answer 31

Enthalpy, h

Question 32

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.

Answer 32

enthalpy of vaporization (or latent heat of vaporization)

Question 33

the ratio of the mass of vapor to the total mass of the mixture

Answer 33

Quality, x

Question 34

A saturated mixture can be treated as a combination of two subsystems:

Answer 34

saturated liquid; saturated vapor

Question 35

Any equation that relates the pressure, temperature, and specific volume of a substance is called an _________

Answer 35

equation of state

Question 36

The simplest and best known equation of state for substances in the gas phase is the _________

Answer 36

ideal gas equation of state

Question 37

_________ is called the gas constant

Answer 37

constant of proportionality R

Question 38

the ideal-gas equation of state, or simply the ideal-gas relation, and a gas that obeys this relation is called an

Answer 38

ideal gas

Question 39

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.

Answer 39

M, the molar mass of the gas

Question 40

An _________ is an imaginary substance that obeys the relation Pv = RT

Answer 40

ideal gas