Monday Jan 13• Roll sheet, please sign• Reading Quiz on 11.3-11.4• Chapter 11

– 11.1 Gases, Liquids, and Solids– 11.2 Intermolecular Forces– 11.3 Select Properties of Liquids– 11.4 Phase Changes

Office Hours

My office is Parmer 324• MWF 10:30-11:30 here in Lewis Hall• Or by appointment (e-mail me)

• Office hours will be posted on the myDU page each week (if there are changes)

Reading for WednesdaySections 11.5-11.6

There will be a Reading Quiz at the beginning of class.

Pre-Class Reading Assignment

Teams – sit class with your teams in class, you may have a different study group outside of

1 Anayeli, Emily Green, Frank, Fernando

2 Yumna, Nicole, Chrisitian, Max

3 Chandler, Alyssa Hernandez, Joseph, Brenda

4 Oliver, Arley, Valerie, Monica

5 Adrian, Jeannette, Miriam, Tezira

6 Catherine Conte, Saman, Evelina, Catherine Trempe

7 Yazmin, Kaitlyn, Jency, Veronica

8 Clayton, Alexandra, Sweta, Camila

9 Alyssa Domico, Matt Kozlowski, Ignacio, Nikita

10 Jacob, Katy, Marissa, Ryan

Chapter 11 Homework

Turn in today– 9, 15, 17, 19, 21, 23, 25, 27

Due Wednesday in class– 33, 35, 39, 45

Due Friday in class – 7, 49, 51, 53, 55, 57, 59, 61, 73

Quiz on section 11.1-11.4 homework problems on Friday Jan. 17 in class.

Polar Covalent Bonds

• When two atoms share electrons unequally, a bond dipole results.

• The dipole moment, , produced by two equal but opposite charges separated by a distance, r, is calculated:

= Qr• It is measured in debyes (D).

From chapter 8

ElectronegativityFrom chapter 8

Difference in Electronegativity tells you about the polarity of the bond

F2 HF LiF

Electronegativity difference

4.0-4.0=0 4.0-2.1=1.9 4.0-1.0=3.0

Type of bond

Non polar covalent

Polar covalent

Ionic

1. If the electronegativity difference (usually called ΔEN) is < 0.5, then the bond is nonpolar covalent.2. If the ΔEN is 0.5 - 1.6, the bond is considered polar covalent3. If the ΔEN is > 2.0, then the bond is ionic.

From chapter 8

Intermolecular Forces Affect Many Physical Properties – example boiling pt

The strength of the attractions between particles can greatly affect the properties of a substance or solution.

Why does acetic acid boil at a higher temperature?

Summarizing Intermolecular Forces

Any questions on 11.1-11.2?

Sample Exercise 11.2

List the substances BaCl2 H2, CO, HF, Ne in order of increasing boiling point

1. Are ions present?2. Is the molecule polar?3. O,N,F bond with H and lone

pair of electrons?4. Molecular weight?

Main topics of 11.3-11.4

1. Viscosity

2. Surface tension

3. Enthalpy of phase changes• Phase change diagram

4. Heating Curve

5. Critical Temperature and Pressure

Viscosity• Resistance of a liquid to flow is

called viscosity.• It is related to the ease with

which molecules can move past each other.

• Viscosity increases with stronger intermolecular forces and decreases with higher temperature.

Surface Tensionresults from the net inward force experienced by the molecules on the surface of a liquid.

Exothermic/Endothermic

• Ice melting is endothermic

• Energy must be put into the system(ice) from surroundings to make ice go from solid to liquid phase

• Energy is need to push molecules farther apart

• Heat of Fusion, DH fus

DH is positive

energy

Phase Changes

DH fus

DH fus

DH vapDH vapDH sub

DH sub

Endothermic – takesEnergy to push molecules farther apart (arrow up red)

Exothermic – energy is released (arrow down blue)

DH freezingDH condensationDH deposition

DH = H final - H initial

DH is positive

DH is negative

Energy Changes Associated with Changes of State

It takes more heat to vaporize substances than to melt them.

DH sub = DH fus + DH vap

Specific heat is the amount of heat energy necessary to increase the temperature of a given mass of a particular substance by some amount

Specific heat =heat transferred

mass temperature change

Cs =q

m T

For liquid water 4.184 J/g-K

Heating Curves

• The heat added to the system at the melting and boiling points goes into pulling the molecules farther apart from each other.

• The temperature of the substance does not rise during a phase change.

• BC• DE

DH fus

DH vap

DH vap

DH fus

DH vap

DH fus

Specific heat of water

Specific heat of gas

Specific heat of ice

Heat added

Cooling CurvesExothermic processDT is negative

Heat added

Cooling CurvesExothermic processDT is negativegas

http://grade9sciencepedagogics.pbworks.com/f/1321228118/Cooling%20Curve%20elearning.png

liquid

solidGas->liquid

Liquidsolid

F

G

H

Sample Ex 11.3

Part A

1.00 mole of ice at -25C to steam at 125 constant pressure 1 atm

Part B

DH• 100g water cooled to

ice at -30.0 oC

Specific heat• H2O(s) 2.03J/gK

• H2O(l) 4.184J/gK

• H2O(g) 1.84J/gK

DH fus 6.01kJ/mol DH vap 40.67kJ/mol

Chapter 11 Homework

Due Wednesday in class– 33, 35, 39, 45

Due Friday in class – 7, 49, 51, 53, 55, 57, 59, 61, 73

Quiz on HW from 11.1-11.4 homework problems on Friday Jan. 17 in class.