Chap 12

1
Chap 12

• Nature of Solids and Liquids

2

• New Seating Chart

3
Essential Questions

• 1. What happens when a substance changes phase
• 2. What are the forces that hold solids and
  liquids together
• 3. What properties can we determine based upon
  these forces

4
Oxygen?(water vapor)Water?sodium
chloride?(ice)

• What is different among these phases?
• What forces hold these substances together in a
  phase?
• Intermolecular
• The nature of the substance determines the kinds
  of intermolecular forces

5
What is the Kinetic Molecular Theory

• A statement that describes the behavior of matter
  in terms of particle motion

6
What are the components of the KMT

• Particles of gases are very small compared to the
  space they occupy
• The particles have no attractions for one another
• Particles are in constant rapid random motion
• Particles travel in a straight line and
  collisions are elastic. (no energy lost)

7

• Lets do the opposite of global warming and make
  a global deep freeze

8
What kinds of solids are there

• ionic- sodium chloride
• Molecular (covalent) dry ice (CO2), organic
  alcohols, etc. We will put the atomic solids in
  this category also.
• Network (covalent) diamond
• metallic,- iron

9
What kind of attractions must be present in order
to make the particles in these stick together to
form the solid

• This depends on the category of the solid.
• Ionic solids (electroneg diff gt1.7) contain ions.
  The attractions are ionic (electrostatic) NaCl,
  KCl, etc. These are strong attractive forces

10

• Ionic solids (electroneg diff ?1.67) contain
  ions.The attractions are ionic (electrostatic)
  NaCl, KCl, etc

11
What kind of attractions must be present in order
to make the particles in these stick together to
form the solid

• Molecular solids are obviously made up of
  molecules (covalent bonding in a discrete
  recognizable particle)Possible Intermolecular
  Attractions are 1.Dispersion (London) 2.
  dipole/dipole 3. H bondingThese are relatively
  weak attractions

12
Molecular Solids
intermolecular
Intramolecular
13
What kind of attractions must be present in order
to make the particles in these stick together to
form the solid

• Network Each atom is covalently bonded to another
  (Diamond.) (One Giant Molecule)

14
NetworkEach atom is covalently bonded to
another (Diamond.) (One Giant Molecule)
15
What kind of attractions must be present in order
to make the particles in these stick together to
form the solid

• Metallic solids metals. (Find these on the
  P.T.) These have metallic bonding. When the
  atoms in a metal float in a sea of mobile
  valence electrons. These are strong bonds but
  non directional

16
Metallic solids metals These have metallic
bonding.
17
What do these attractions do

• The more attractions the stronger the forces
  holding the substance together
• This determines the melting point, boiling point,
  vapor pressure, etc.
• You will not have to determine the absolute
  values but the relative values.

18
How do they vary

• We mentioned before they vary in strength.The
  stronger the attractions (bonds) the more energy
  to overcome those attractions and the higher
  m.p., b.p., etc it will have.
• These attractions are cumulative. (The more
  attractions present, the stronger the forces
  holding the substance together)

19
What are the properties of Ionic substances

• high m.p.
• High b.p.
• brittle
• nonconductor as solid solids but conductor as
  liquid

20
What are the properties of Molecular substances

• Because these forces are relatively weak they
  generally, they have low m.p., Low b.p.,Soft,
  nonconductor (insulator)

21
These vary though depending on the type of
covalent bonds present, the shape and size of the
molecule. There are 3 possible forces present
that determine these properties.

• 1 London dispersion forces. These depend upon the
  size, shape. All molecules (and atoms) have
  dispersion forces.

22
London dispersion forces
These occur between all molecules. It is the
only attraction between nonpolar molecules
23
Dispersion (London) forces
24
Dispersion (London) forces depend uponsize,
shape

• The larger the molecule, the greater the
  attractions
• The more symmetrical the molecule (the better it
  can fit together)
• the greater the attractions

25
Dipole-DipoleOccurs in polar molecules(Depends
on shape and nonbonded electrons)
26
Hydrogen bonding occurs only between the
hydrogen of one molecule and the O, N, and F of
anotherhere is water
27
What is special about these

• They only work when the molecules are close
  together(only good for short distances) the more
  of the attractions possible the greater the
  forces will be holding the molecules together.
  The larger the molecule the greater the
  attractions

28
Lets look at some molecules
Substance kind of forces present

• H2O H-bondingdipole-dipole
  Dispersion
• SO2 dipole-dipoleDispersion (no H
  bonding)
• Cl2 Dispersion (no H, no dipole)
• H2 Dispersion

29
Now lets rank them in order of greatest
attractions to least.

• H2O most because it has all 3 possible
  attractive forces.(H-bonding dipole-dipoledisp).
  The key here is H bonding is a lot stronger than
  the others.
• SO2 next because it has 2 of the forces
  .dipole-dipole (polar) Disp
• Cl2 next London(no H, no dipole)
• H2 last London(smallest) lowest m.p(b.p.)

30
How can we decide between these last two?

• Since they both have only dispersion they are
  the weakest but Chlorine is much larger than
  hydrogen and the larger the molecule the greater
  the attractions

31
What are the properties of network substances

• very high m.p.
• Very high b.p.
• very hard
• Nonconductor (insulator)

32
Why

• Every atom has a covalent bond connecting it to
  another. Covalent bonds are very strong

33
You know the Properties of metals

• high m.p.,b.p. good conductor, maleable, ductile,
  lusterous

34
How can we predict the phases of substances at
room temp

• The more attractions a substance has the higher
  the temp has to be to get it to melt and then
  boil.

35
So how am I supposed to do this

• Ionic and metallic and network (special kind of
  covalent) have very strong attractions and will
  be solids at room temp
• covalent (molecules) gases at room temp unless
  you have experience that tells you otherwise.
  (water, alcohols, large organics octane,) Small
  covalent nonpolar (molecules) substances have
  almost no attractions and are gases at room temp.

36
For each of the followingClassify, describe the
properties, determine the attractive forces,
determine the phase at room temp
PCl3, its a molecule (lt1.7 diff) so it has
Disperion. If you draw the molecule you will find
there is 1 lone pair on P so it is polar and
therefore there is Dipole-dipole attract. No Hs
so no H bonding.It is low m.p/b.p., soft,
insulatorThis will be a gas.

• PCl3

He
Disp only- same prop as PCl3. gas
37
For each of the followingClassify, describe the
properties, determine the attractive forces,
determine the phase at room temp
Molecule so Disp, polar bond so dipole, and H and
F so H bonding. Same as two above. gas

• HF

ionic solid. Electrostatic. high m.p., high
b.p. brittle nonconductor as solid solids but
conductor as liquid
Li2O
Metallic, Electrostatic. conductor, maleable,
ductile, high m.p solid
Cu
38
Rank in order of m.p.

• Highest (ionic)

NaCl, CH4, H2O
Lowest (molecular, disp)
Middle (molecular, disp, dip-dip, H bonding)
39
What is vapor pressure

• Vapor Pressure. If the vapor is allowed to escape
  it is called evaporation. (The high energy
  particles at the surface leave and the remaining
  particles now have a lower average K.E. and
  therefore a lower temp. Evaporation cools you
  off)

40
Vapor Pressure In order for a liquid the strength
of these forces to become a gas, it must overcome
the forces holding the particles together in the
liquid phase
41
What is a volatile liquid?Give an example of
one.

• One that has high vapor pressure (evaps easily)
• fingernail polish remover
• perfume

42
What is Viscosity

• Resistance to flowThe more attractions between
  the particles in a liquid, the greater the
  viscosity

43
How does temp affect

• Decreased temp puts the particles closer together
  which increases the attractive force. Also
  decreases the energy of the particles so they
  have less energy to overcome the
  forces.Increasing temp is the opposite

44
Surface Tension

• The imbalance of forces at the surface of liquids
  that cause it to act as if there was a film
  stretched across it

45
What is cohesion

• The force of attraction between identical
  molecules

46
What is adhesion

• The force of attraction between different
  molecules

47
What do these have to do with capillary action

• Capillary action is when the surface of a liquid
  is observed to be elevated or depressed where it
  comes into contact with a solid. Capillarity can
  be explained by considering the effects of two
  opposing forces adhesion, and cohesion.
  Adhesion causes water to wet a glass container
  and thus causes the water's surface to rise near
  the container's walls. If there were no forces
  acting in opposition, the water would creep
  higher and higher on the walls and eventually
  overflow the container. The forces of cohesion
  act to minimize the surface area of the liquid
  when the cohesive force acting to reduce the
  surface area becomes equal to the adhesive force
  acting to increase it , equilibrium is reached
  and the liquid stops rising where it contacts the
  solid.
• In some liquid-solid systems, e.g., mercury and
  glass or water and polyethylene plastic, the
  liquid does not wet the solid, and its surface is
  depressed where it contacts the solid.
• Capillarity is one of the causes of the upward
  flow of water in the soil and in plants.

48
How is evaporation different from Boiling

• Evaporations occurs only at the surface
• Boiling occurs everywhere within the liquid.
• Evaporation occurs at all temperatures(below b.p.

49
List the 6 unusual properties of water, primarily
due to its POLARITY.

• 1. high boiling pt2. high specific heat capacity
  (absorb a lot of heat w/o increasing temp much3.
  ice less dense than water4. high surface
  tension5. high heat of vaporization6. Universal
  solvent

50
How do these properties account for water being
so vital to living things?

• moderates world temp, cools, keeps lakes from
  freezing,