CHAPTER 13 LIQUIDS & SOLIDS

CHM 130

GCC

13.1 13.1 Properties of Properties of

LiquidsLiquids1. Liquids take the shape of their container,

but have a constant volume.

2. Different liquids flow at different rates. (Viscosity)

3. Liquids are not compressible since the atoms/molecules are close together.

4. Liquids have much higher densities than gases.

5. Soluble liquids will mix uniformly together.

13.2 IMFBONDS hold atoms together within a single molecule. (Polar and nonpolar covalent bonds)

Review polar and nonpolar bonds and molecules

INTERMOLECULAR FORCES (IMF) hold molecules together in liquids and solids.

–IMF are always weaker than bonds!

Bonds vs IMFBonds vs IMF

In one HCl molecule what holds the H to the Cl is

a polar covalent bond. H-Cl

In a sample with thousands of HCl molecules what holds them together is IMF.

H-Cl H-Cl

INTERMOLECULAR FORCESINTERMOLECULAR FORCES

1) Dispersion (London) Forces1) Dispersion (London) Forces

2) Dipole-Dipole Forces 2) Dipole-Dipole Forces

3) Hydrogen Bond Forces3) Hydrogen Bond Forces

H bond forces is NOT a bond!!!H bond forces is NOT a bond!!!

Dispersion (London) Force• Temporary attraction between nonpolar

molecules or atoms that form when two of them get real close.

• Electrons get pushed to one side so results in a temporary partial negative charge (-) that disappears when the molecules separate.

• Often seen in gases since very little attraction between nonpolar molecules – thus they are not close together but far apart (gas)!!!

• Bigger molecules, more electrons, more London Force.

Two Nonpolar Molecules

Dipole – Dipole forces• Exists between polar molecules. Exists between polar molecules. (have partial (have partial

+ and + and – ends)– ends)• The partial The partial + end of one molecule is + end of one molecule is

attracted to the partial attracted to the partial - end of a second - end of a second molecule (opposites attract).molecule (opposites attract).

H Cl

-

H Cl

+ +

-

Dipole-Dipole Forces• Stronger than London forces.

• Must be POLAR molecules.

Hydrogen Bonding Force

• An especially strong dipole force between An especially strong dipole force between molecules containing the molecules containing the very polarvery polar H-F, H-F, H-O or H-N bonds.H-O or H-N bonds.

• The The + H end of one molecule is attracted + H end of one molecule is attracted to the to the - N/O/F end of a second molecule. - N/O/F end of a second molecule.

H Bond Force• Strongest type of IMF, yet still much

weaker than a bond.

Polar covalent bonds

Indicate the strongest type of IMF between

these molecules:

Polar or Nonpolar?

Strongest Intermolecular Force

CO2

PF3

HF

CH4

nonpolar

polar

polar

nonpolar

London

Dipole - Dipole

H Bond Force

London

Bonds vs Forces

• Bonds– Ionic bond (holds metal/nonmetal ions together)– Polar Covalent Bond (e- shared unequally

between nonmetal atoms)– Nonpolar Covalent Bond (e- shared equally)

• Forces– London (nonpolar molecules)– Dipole Dipole (polar molecules)– H bond Force (H bonded to NOF)

Coulomb’s Law Review• Opposite charges attract according to Coulomb’s

Law• The electrostatic attraction between two charges is

proportional to the charge magnitude (q) and inversely proportional to the distance (r) squared.

• F = ke(q1q2 / r2)• Larger charge means stronger attraction!• Ionic bonds very strong cause charges are

complete +1, +2, +3 charges. Like in NaCl. • Dipole dipole IMF much weaker cause charges are

much less than +1. Remember polar bonds are partially + and -.

Choose the bond or IMF described for each below:

Bond or IMF? What holds these together???

What holds the atoms together in one ammonia NH3 molecule?

What is holding the H and O atoms together in water?

What is holding three HCl molecules together?

What is holding the ions together in salt NaCl.

What is holding four H2O molecules together.

What holds nitrogen gas molecules to each other?

What is holding the O’s together in an oxygen gas molecule?

What is holding two ammonia molecules together?

Answers on Next Slide

Choose the bond or IMF described for each below:

Bond or IMF? What holds these together???

Polar covalent bonds

What holds the atoms together in one ammonia, NH3, molecule?

Polar covalent bonds

What is holding the H and O atoms together in water?

Dipole Dipole forces

What is holding three HCl molecules together?

Ionic bonds What is holding the ions together in salt NaCl.

H bonding forces

What is holding four H2O molecules together.

London forces What holds nitrogen gas molecules to each other?

Nonpolar covalent bonds

What is holding the O’s together in an oxygen gas molecule?

H bonding forces

What is holding two ammonia molecules together?

13.3 Vapor Pressure (VP)13.3 Vapor Pressure (VP)• At the surface of a liquid some

molecules have enough kinetic energy to break the attractive forces (IMF) with neighboring molecules.

• They escape from the liquid and go into the gas state.

• If no lid, they float away with air molecules.

• If there is a lid, a pressure develops.

Vapor Pressure is the pressure exerted by gas molecules above a liquid in a closed container.

• Stronger IMF higher or lower VP ???

Which has weaker

IMF? Higher VP?

A

–Lower. Stronger attractions mean less likely to break away from surface and go into gas state (so less gas so less pressure)

A

Balloons are attached to flasks containing water and ether. Which has stronger IMF? Higher VP?

Water has stronger IMF and it stays together as liquid. Ether has low IMF, molecules break away into gas filling balloon, so it has higher VP.

Boiling Point (bp)

Temperature where liquid changes to gas.

Stronger IMF = higher or lower bp ??

– Higher – Strong IMF means molecules held tightly together so more energy is required to pull them apart so need higher temp.

Surface TensionSurface Tension• Surface molecules hold on to each other,

this is why liquids make drops / beads.

• Stronger IMF = high or low surface tension?

High – stronger IMF means molecules are attracted so molecules stay together with more

surface tension.

Surface TensionSurface TensionWhich drop of liquid has higher IMF

& surface tension?

A, because molecules held together and did not spread out very much

VISCOSITYVISCOSITYThe resistance of a liquid to flow.

• Oil flows slowly high viscosity

• Vodka flows rapidly low viscosity

Stronger IMF higher or lower viscosity ???

Higher because molecules held together so flow is hindered and slow.

Let’s compare ammonia and fluorine. First what IMF do they have?

NH3 has H bonding force, F2 gas has

London forceQuestions

1. Which has stronger IMF?2. Which has the lower bp?3. Which is polar?4. Which has higher VP?5. Which is least viscous (if liquid)?6. Which has more surface tension?

AmmoniaFluorine

AmmoniaFluorineFluorine

Ammonia

Fill in the blanks with increase or decrease

• As IMF increase:– Viscosity ____________– Bp ___________– Surface tension ___________– Vapor pressure ___________

increasesincreases

increasesdecreases

13.4 Properties of Solids13.4 Properties of Solids• Solids have a fixed shape and volume.• Solids are crystalline or noncrystalline.• Solids are not compressible - particles are

close together.• Most solids have a slightly higher density

than their liquid state. Solids sink in their liquid.

– Ice is an important exception since ice is actually less dense than water. Ice floats in water.

• Solids do not mix by diffusion or osmosis.

13.5 Crystalline solids13.5 Crystalline solids- Solid arranged

in a specific order.

- Crystalline solids have regular geometric shapes / patterns like hexagonal

Cu

Emerald

Quartz

Glucose

SOLIDSSOLIDSType Particles mp & bp Other properties Ex.

Ionicmetal cations & nonmetal

anionsHigh

hard, brittle,some soluble in water,conduct electricity when melted or dissolved in water

KClAgBrCaF2

MgCl2

Molecularnonmetal atoms or

moleculesLow

usually insoluble in water, do not conduct electricity

S8

Dry ice

Metallic

metal atoms surrounded by "sea of electrons"

Varies

malleable, ductile,insoluble in most liquid solvents,conduct electricity

silverzinc

Salt NaCl

Copper

Ice

13.6 HEATING CURVE13.6 HEATING CURVE

HEATING CURVEHEATING CURVET (

C)

Heat Added

solid

s l

liquid

l g

gas

mp

bp

13.7 Structure of Water13.7 Structure of Water

H2O has a bent molecular geometry with a bond angle less than 109.5

1. Water has very polar O-H bonds: can dissolve many ionic compounds and mix with other polar substances

2. Water has strong H bond Forces between molecules.

13.8 Properties of water13.8 Properties of water

•Very polar, high IMF

•Low vapor pressure

•Unusually High bp & mp: bp=100C, mp=0C

•High surface tension

•Water expands as it freezes Density of ice is less than density of liquid water ( really rare and odd)

For Fun• Henry’s Law http://www.youtube.com/watch?v=8yU5y-

cFXoo&feature=related

• Solubility of a gas in a liquid increases as P increases, and decreases as P decreases

• When you open soda can, you decrease the pressure, and some CO2 gas comes out of solution as bubbles (solubility decreased)

• The Bends http://www.youtube.com/watch?v=0ixYDJAYOYk

Self Test

• Page 382

• Try 1-5, 11-13

• Answers in Appendix J