intermolecular forces
DESCRIPTION
Intermolecular Forces. Forces Between Molecules. Why are intermolecular forces important?. They determine the phase of a substance at room temperature. (Competition with kinetic energy.). Solids. Strong Intermolecular Forces. Gases. Weak Intermolecular Forces. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/1.jpg)
Intermolecular Forces
Forces Between Molecules
![Page 2: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/2.jpg)
Why are intermolecular forces important?
They determine the phase of a substance at room temperature. (Competition with kinetic energy.)
![Page 3: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/3.jpg)
Solids
Strong Intermolecular Forces
![Page 4: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/4.jpg)
Gases
Weak Intermolecular Forces
![Page 5: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/5.jpg)
3 Types of Intermolecular Forces
Dispersion or Van der Waals Dipole-dipole
Hydrogen Bonds
![Page 6: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/6.jpg)
Strongest Intermolecular Force
Hydrogen Bonds
![Page 7: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/7.jpg)
Hydrogen Bonds
![Page 8: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/8.jpg)
When do Hydrogen bonds occur?
Between molecules containing F, O, N bonded to a
H atom
![Page 9: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/9.jpg)
Strongest hydrogen bonds?
Between molecules containing F-H bonds
![Page 10: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/10.jpg)
Weakest hydrogen bonds?
Between molecules containing N-H bonds
![Page 11: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/11.jpg)
What effect does H-bonding have on the properties of the
substance?
Hydrogen bonding leads to substantial increases in the
expected boiling point.
![Page 12: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/12.jpg)
Weakest Intermolecular Force
Dispersion or Van der Waals forces
![Page 13: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/13.jpg)
When do dispersion forces occur?
Occur between all molecules. Most important between
nonpolar molecules
![Page 14: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/14.jpg)
Nonpolar
No Poles!The molecule is symmetric!
Cannot tell 1 end from the other.
![Page 15: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/15.jpg)
2 Easy categories of Nonpolar Molecules
Monatomic Gases (Column 18)(kickballs)
&Diatomic Elements
(H2, N2, O2, F2, Cl2, Br2, I2)(footballs)
![Page 16: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/16.jpg)
2 More Easy categories of Nonpolar Molecules
Hydrocarbons(CxHy)
&Small symmetric molecules(CO2, CS2, CF4, CBr4, etc.)
![Page 17: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/17.jpg)
What are the diatomic elements?
H2, N2, O2, F2, Br2, Cl2, & I2
![Page 18: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/18.jpg)
What can you say about dispersion forces as a
function of molecular size?
The larger the molecules the stronger the dispersion
forces!
![Page 19: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/19.jpg)
When do dipole-dipole forces occur?
Between polar molecules.Permanent separation of charge.
1 side - (electron rich) vs. 1 side + (electron poor)
![Page 20: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/20.jpg)
Polar
Has Poles!The molecule is NOT
symmetric!Can tell 1 end from the other.
![Page 21: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/21.jpg)
Vapor
Gas phase of a substance that is normally a liquid at room
temperature.
![Page 22: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/22.jpg)
Vapor Pressure
The partial pressure of a vapor above its liquid.
![Page 23: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/23.jpg)
What does vapor pressure depend on? (Hint: see Table
H)
Vapor pressure depends on the temperature of the liquid.
![Page 24: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/24.jpg)
What happens to the vapor pressure as the temperature of
the liquid is increased?
The vapor pressure always increases with temperature.
![Page 25: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/25.jpg)
Does the vapor pressure depend on the amount of
liquid present?
No. A thimbleful is as good as an ocean.
![Page 26: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/26.jpg)
What are some differences between evaporation &
boiling?
Evaporation occurs at all temperatures. Boiling occurs at a
definite temperature. Evaporation occurs at the surface.
Boiling occurs throughout the liquid.
![Page 27: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/27.jpg)
Heat of fusion
Amount of energy required to convert 1 gram of a pure solid to
the liquid phase at its melting point.
![Page 28: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/28.jpg)
Heat of vaporization
Amount of energy required to convert 1 gram of a pure liquid to the gas phase at its boiling
point.
![Page 29: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/29.jpg)
What happens to the boiling point as the intermolecular
forces increase?
The stronger the intermolecular forces, the higher the boiling point.
![Page 30: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/30.jpg)
What happens to the melting point as the intermolecular
forces increase?
The stronger the intermolecular forces, the higher the melting point.
![Page 31: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/31.jpg)
What happens to the heat of fusion as the intermolecular
forces increase?
The stronger the intermolecular forces, the higher the heat of fusion.
![Page 32: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/32.jpg)
What happens to the heat of vaporization as the
intermolecular forces increase?
The stronger the intermolecular forces, the
higher the heat of vaporization.
![Page 33: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/33.jpg)
What happens to the evaporation rate as the intermolecular forces
increase?
The stronger the intermolecular forces, the
lower the evaporation rate.
![Page 34: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/34.jpg)
What happens to the vapor pressure as the intermolecular
forces increase?
The stronger the intermolecular forces, the lower the vapor pressure.
![Page 35: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/35.jpg)
Pre
ssu
re,
atm
Temperature, C
![Page 36: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/36.jpg)
Relationship between IMF and physical properties?
IMF BP MP Hf HvEv.Rt V.P.
IMF BP MP Hf Hv EvRt VP
![Page 37: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/37.jpg)
Boiling Point
Temperature at which the vapor pressure of a liquid is
equal to the external pressure.
![Page 38: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/38.jpg)
Normal Boiling Point
Temperature at which the vapor pressure of a liquid is
equal to 1 atm or 101.3 kPa or 760 torr.
![Page 39: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/39.jpg)
What happens to the boiling point when the external
pressure is reduced?
The boiling point is reduced.
![Page 40: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/40.jpg)
Sublimation
Solid to gas
![Page 41: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/41.jpg)
Deposition
Gas to solid
![Page 42: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/42.jpg)
Vaporization
Liquid to Gas
![Page 43: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/43.jpg)
Condensation
Gas to liquid
![Page 44: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/44.jpg)
Fusion
Solid to liquidOr
Melting
![Page 45: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/45.jpg)
Freezing
Liquid to solidCrystallizationSolidification
![Page 46: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/46.jpg)
Which phase changes are endothermic?
Solid to liquidLiquid to GasSolid to Gas
G
L
S
![Page 47: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/47.jpg)
Which phase changes are exothermic?
Gas to LiquidLiquid to SolidGas to Solid
G
L
S
![Page 48: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/48.jpg)
Given 3 substances at room temperature: 1 solid, 1 liquid, & 1 gas, which has the strongest intermolecular forces?
Solid > Liquid > Gas
![Page 49: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/49.jpg)
Describe the mp & bp of gases.
Low!
![Page 50: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/50.jpg)
What happens to the temperature as heat is added to a substance at its melting or boiling point?
Nothing, until the phase change is complete. The heat
energy is going into the potential energy of the
system.
![Page 51: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/51.jpg)
HF
HF
--------
Hydrogen Bonding!
![Page 52: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/52.jpg)
Ne
Ne
--------
Van der Waals or dispersion forces
![Page 53: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/53.jpg)
H-Cl
H-Cl
--------
Dipole-dipole forces
![Page 54: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/54.jpg)
H-N
H-F
--------
Hydrogen Bonding
H H--
OH
H
-
-----------
----
---
![Page 55: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/55.jpg)
Time
Tem
pera
tur
e
I II III IV V
Solid
Solid & Liquid
Liquid
Liquid & Gas
Gas
K.E. K.E. K.E.
K.E.↔K.E.↔P.E.↔
P.E.↔P.E.↔
P.E.P.E.Melt pt.
Boil pt.
![Page 56: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/56.jpg)
Equation for a pure substance in a single phase being warmed up or cooled down.
Q = mCTQ = energy in Joulesm = mass in grams
C = specific heat in J/gT = temperature change
![Page 57: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/57.jpg)
Equation for a substance melting or freezing at the freezing point.
Q = mHf
Q = energy in Joulesm = mass in gramsHf = heat of fusion
![Page 58: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/58.jpg)
Equation for a substance boiling or condensing at the boiling point.
Q = mHv
Q = energy in Joulesm = mass in grams
Hv = heat of vaporization
![Page 59: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/59.jpg)
Temperature of the ice-water equilibrium.
0C or 273KFreezing pointMelting point
![Page 60: Intermolecular Forces](https://reader035.vdocuments.us/reader035/viewer/2022062301/56814dbc550346895dbb12a5/html5/thumbnails/60.jpg)
Temperature of the steam-water equilibrium.
100C or 373KBoiling point
Condensation point