Topic 3 Flashcards
Evaluating Properties
Substance that has a fixed chemical
composition throughout
Pure Substance
A mixture of various chemical
elements or compounds also
qualifies as a pure substance as long
as the mixture is
Homogeneous
Does not have to be of a single
chemical element or compound.
Pure Substance
Major Components in Dry Air
Nitrogen - 78.08%
Oxygen - 20.95
Argon - 0.93%
Other - 4%
Minor Components in Dry Air (Other 4%)
Carbon Dioxide - 0.033%
Neon - 0.0018%
Helium - 0.0005%
Methane - 0.0002%
Krypton - 0.0001%
Hydrogen - 0.00005%
Xenon - 0.000009%
any mixture that is uniform in
composition throughout.
Homogeneous mixture (solutions)
3 principal phases
Solid, Liquid, Gas
quantity of matter that is
homogeneous throughout in both
chemical composition and physical
structure
Phase
strong intermolecular bond
Solid
intermediate intermolecular bonds
Liquid
weak intermolecular bond
Gas
the temperature and pressure above which there is no distinction between the liquid and vapor phases.
Critical Point
the temperature and pressure at which all three
phases can exist in equilibrium.
Triple Point
change of phase from solid to vapor.
Sublimation
change of phase from liquid to vapor.
Vaporization
change of phase from vapor to liquid.
Condensation
change of phase from solid to liquid.
Fusion or Melting
a point on a phase diagram at which both the liquid and gas phases of a substance have the same density, and are therefore indistinguishable.
Critical Point
condition in which a mixture of vapor
and liquid can exist together at a given
temperature and pressure.
Saturation
the pressure at which the liquid and
vapor phases are in equilibrium at a
given temperature
Saturation pressure
Saturation
For a pure substance there is a
definite relationship between
saturation pressure and saturation
temperature.
The higher the pressure, the higher
the saturation temperature
If a substance exists as a liquid at the
saturation temperature and pressure
Saturated Liquid
If the temperature of the liquid is
lower than the saturation temperature
for the existing pressure
sub cooled liquid or compressed liquid.
If a substance exists entirely as
vapor at saturation temperature
Saturated Vapor
When the vapor is at a temperature
greater than the saturation temperature
Superheated vapor
Pressure and temperature of
superheated vapor
- are independent properties,
- temperature may increase while
the pressure remains constant
amount of energy absorbed or released during a phase-change process.
Latent Heat
Latent heat of fusion
- amount of energy absorbed during
melting. - equivalent to the amount of energy
released during freezing.
Latent heat of vaporization
- amount of energy absorbed
during vaporization - equivalent to the energy
released during condensation.
Latent Heat
At 1 atm pressure
latent heat of fusion of water
333.7 kJ/kg
latent heat of vaporization
2256.5 kJ/kg.
ratio of the mass of the vapor to the
total mass of both vapor and
liquid.
Quality
Quality
When a substance exists as part liquid
and part vapor at saturation conditions
Moisture Content
The moisture content of a substance
is the opposite of its quality.
defined as the ratio of the mass
of the liquid to the total mass of
both liquid and vapor
Moisture content
any extensive property
Y
corresponding intensive property
y
v < vf
Compressed Liquid
vf < v < vg
Saturated Liquid
v > vg
superheated
x = 0.0
Saturated Liquid
states the pressure of a gas expanding
at constant temperature varies
inversely to the volume,
Ideal Gas Law
Robert Boyle
Ideal Gas Law
P1V1 = P2V2 = constant
Jacques Charles
concluded that the pressure of a gas varies directly with temperature when the volume is held constant, and the volume varies directly with temperature when the pressure is held constant
Jacques Charles
V1 / V2 = T1 / T2 or P1 / P2 = T1 / T2
universal gas constant
Ru
R = Ru / M
Specific heat at constant volume
Cv (for a constant-volume process)
Specific heat at constant pressure
Cp (for a constant - pressure process)
specific heat ratio
k
k = Cp / Cv
functions of temperature alone
u, h, Cv, and Cp
