13 15 1-15 3
Lecture . .
-Molecules
insolids/liquids
reclose to each
other
molecules constant
traveling lines and
rotating / vibrating
·
in
gases are in motion in
straight
freely
↳
avg distance btun molecules is large gases
= have low densities
↳ volume of
gas volume of container
=
molecules solids are close together and fixed positions, do vibrate in
they
·
in in
this fixed position
·
Molecules in liquid are also close
together but not fixed they ,
rotate and move
throughout fluid
↳ translational and rotational mumt in
liquids is hindred by the frequent
collisions of the molecules
#distence btwn molecules in solids /liquids is much smaller than in
gases
*
·
molar volume indication of average
:
separation btun molecules
molar volume solid moler volume liquid Tempere
·
Altrap
"HO(g)
25
i
s
100-
-Melting/Boiling
↳
heating
H20(1) + H20 (g)
on a curve
75-
heating curve shows how substance varieswI time
·
as it is heated at a constant rate Stop
molar
enthalpy of fusion-energy absorbed
·
as
heat that is required to melt one moreof any
o
-
18
substance
↳
AHaus (timeto meltore mole (min(mol)) (heat added (5/min)
=
moler heat of vaporization energy absorbed as heat needed to vaporize one
more of a substance
↳
DHrap (time to raporizeonemole (min/mol)(heat added (5/mink)
=
15
·
3-Energy
.
melting of one mole
energy as
vaporization of
heat
is required
of
required
one more
any
to melt I
substance
to melt
vaporize
n
is denoted
moles of substance:
of any substance is
by Nis) Nie
:
denoted by XX ,g)
Altars
GGsn(DHrus]- negative when
:
Altrap
positive value
when melting,
freezing
·a
q
q
-
I
:
herformulas
:
nCAT
cDT
(a)
Positive value when
·
energy as heat required to vaporize n moles of substance :
quap
:
n/Altvap -
>
vaporizing negative ,
·
sublimation-solid converting directly to a
when
condensing
gas
Alsub energy absorbed mole of solid sublimed
·
:
as heat when one is at constant pressure
↳
Example :
dry ice-(O2(s)-(O2(g) Alsub 25 2:
.
, Lecture 2 + 15 4 15 5 .
,
.
-
15 4e Van der Waals
.
Forces
higher values of Altrap Altsob the molecules of the solid liquidwe attracted to
·
or mean or more
each other
it takes lot of to
opposite changes of
·
energy separate ions
a
↳
molar enthalpies of vaporization are much
larger for ionic compounds than nonionic compounds
↳ for ionic
·
boiling points are also
higher compounds It takes more
dipole-dipole attraction attracted to another
·
molecules
polar one
:
are
↳
dipole dipole forces are weaker than ionion forces as
interaction energies between
3
intermolecular forces
-
: forces between neutral molecules neutral molecules are much weaker than intermolecular
than the covalent bonds
-
intramolecular forces forces : within molecule (i e chemical bones) forces
-
a .
within the molecule
hydrogen bond the electrostatic attraction between
:
hydrogen atom and a
highly electronegative atom /like O, N ,
FI
↳
open structure of ice due to Hatom bonding to adjacent O atom,
giving a tetrahedral shape I bonds are
↳ when dipole dipole bonds
melts , it loses someIt to increased density
ice hands,
leading on steroids
↳H
bonds also occur in NHz ,
but the force is weaker than water because
nitrogen is less
electronegative than oxygen
London forces :
a
type of IMF that acts on molecules that have electrons dispersed symmetrically
with the nucleus (all molecules have if asked to list IMFs , aways start wl LDF a guarentee t
,
der Waals forces
van : attractive forces between molecules (dipose dipose or london forces) j
S S
smaller surface area
15-3
Viscosity Surface Tension Capillary Action means lower LDF small
+
, , ,
viscosity of liquids resistance to flow intermolecular forces
·
a measure
:
a
↳ &
flowing smoothly :
viscous 111
c-c i i Or co -
C
-4 -
- - -
↳
increased temperative decreased viscosity "
11 1
larger LDF small LDF
surface tensions molecules at the surface of liquid experience net attractive forces towards the interior surface tension and the
,
causing
molecule to afloat
stay
agents (surfactals
↳
surface acting -
lower surface tension of a liquid by concentrating at the surface
capillaryoon
thin tube
capillary action of liquid
·
:
rise a
through a
·
shape formed by a liquid in
meniscus there
polarity "Like dissolves like"
·
:
molecules with weak IMFs will be to vaporize
·
easier
Lecture . .
-Molecules
insolids/liquids
reclose to each
other
molecules constant
traveling lines and
rotating / vibrating
·
in
gases are in motion in
straight
freely
↳
avg distance btun molecules is large gases
= have low densities
↳ volume of
gas volume of container
=
molecules solids are close together and fixed positions, do vibrate in
they
·
in in
this fixed position
·
Molecules in liquid are also close
together but not fixed they ,
rotate and move
throughout fluid
↳ translational and rotational mumt in
liquids is hindred by the frequent
collisions of the molecules
#distence btwn molecules in solids /liquids is much smaller than in
gases
*
·
molar volume indication of average
:
separation btun molecules
molar volume solid moler volume liquid Tempere
·
Altrap
"HO(g)
25
i
s
100-
-Melting/Boiling
↳
heating
H20(1) + H20 (g)
on a curve
75-
heating curve shows how substance varieswI time
·
as it is heated at a constant rate Stop
molar
enthalpy of fusion-energy absorbed
·
as
heat that is required to melt one moreof any
o
-
18
substance
↳
AHaus (timeto meltore mole (min(mol)) (heat added (5/min)
=
moler heat of vaporization energy absorbed as heat needed to vaporize one
more of a substance
↳
DHrap (time to raporizeonemole (min/mol)(heat added (5/mink)
=
15
·
3-Energy
.
melting of one mole
energy as
vaporization of
heat
is required
of
required
one more
any
to melt I
substance
to melt
vaporize
n
is denoted
moles of substance:
of any substance is
by Nis) Nie
:
denoted by XX ,g)
Altars
GGsn(DHrus]- negative when
:
Altrap
positive value
when melting,
freezing
·a
q
q
-
I
:
herformulas
:
nCAT
cDT
(a)
Positive value when
·
energy as heat required to vaporize n moles of substance :
quap
:
n/Altvap -
>
vaporizing negative ,
·
sublimation-solid converting directly to a
when
condensing
gas
Alsub energy absorbed mole of solid sublimed
·
:
as heat when one is at constant pressure
↳
Example :
dry ice-(O2(s)-(O2(g) Alsub 25 2:
.
, Lecture 2 + 15 4 15 5 .
,
.
-
15 4e Van der Waals
.
Forces
higher values of Altrap Altsob the molecules of the solid liquidwe attracted to
·
or mean or more
each other
it takes lot of to
opposite changes of
·
energy separate ions
a
↳
molar enthalpies of vaporization are much
larger for ionic compounds than nonionic compounds
↳ for ionic
·
boiling points are also
higher compounds It takes more
dipole-dipole attraction attracted to another
·
molecules
polar one
:
are
↳
dipole dipole forces are weaker than ionion forces as
interaction energies between
3
intermolecular forces
-
: forces between neutral molecules neutral molecules are much weaker than intermolecular
than the covalent bonds
-
intramolecular forces forces : within molecule (i e chemical bones) forces
-
a .
within the molecule
hydrogen bond the electrostatic attraction between
:
hydrogen atom and a
highly electronegative atom /like O, N ,
FI
↳
open structure of ice due to Hatom bonding to adjacent O atom,
giving a tetrahedral shape I bonds are
↳ when dipole dipole bonds
melts , it loses someIt to increased density
ice hands,
leading on steroids
↳H
bonds also occur in NHz ,
but the force is weaker than water because
nitrogen is less
electronegative than oxygen
London forces :
a
type of IMF that acts on molecules that have electrons dispersed symmetrically
with the nucleus (all molecules have if asked to list IMFs , aways start wl LDF a guarentee t
,
der Waals forces
van : attractive forces between molecules (dipose dipose or london forces) j
S S
smaller surface area
15-3
Viscosity Surface Tension Capillary Action means lower LDF small
+
, , ,
viscosity of liquids resistance to flow intermolecular forces
·
a measure
:
a
↳ &
flowing smoothly :
viscous 111
c-c i i Or co -
C
-4 -
- - -
↳
increased temperative decreased viscosity "
11 1
larger LDF small LDF
surface tensions molecules at the surface of liquid experience net attractive forces towards the interior surface tension and the
,
causing
molecule to afloat
stay
agents (surfactals
↳
surface acting -
lower surface tension of a liquid by concentrating at the surface
capillaryoon
thin tube
capillary action of liquid
·
:
rise a
through a
·
shape formed by a liquid in
meniscus there
polarity "Like dissolves like"
·
:
molecules with weak IMFs will be to vaporize
·
easier
