Post on 26-Dec-2015
States of Matter
Chapter 13
Matter
Let’s get to the heart of it…
The particles are in constant motion
Kinetic-Molecular Theory Describes the motion of individual
molecules Kinetic = “to move” Also called Kinetic Theory
Forces of Attraction Affect on States of Matter
At room temperature (20oC-25oC, 68oF-77oF) all particles of matter have the same kinetic energy
So why do we have different states of matter for these materials?
There are different strengths of INTERMOLECULAR FORCES
13.2 Forces of Attraction
Intermolecular ForcesWhat holds molecules together
Intermolecular Forces
They are what make solid and liquid molecular compounds possible.
The weakest are called van der Waal’s forces - there are two kinds Dispersion forces (London forces) Dipole Interactions
Dispersion Force
Depends only on the number of electrons in the molecule
Bigger molecules more electrons More electrons stronger forces
F2 is a gas
Br2 is a liquid
I2 is a solid
All are nonpolar but why are they different states of matter?
Dispersion force
H H H HH H H H
+ -
H H H H
+ - +
Dispersion Force Occurs between all molecules
Depends only on the number of electrons in the molecule
Result from a temporary shift in density of electrons in electron clouds
Causes nonpolar molecule to become polar
Happens quickly and temporarily for nonpolar molecules
Dipole interactions
Occur when polar molecules are attracted to each other.
Slightly stronger than dispersion forces.
Opposites attract but not completely hooked like in ionic solids.
Dipole interactions
Occur when polar molecules are attracted to each other.
Slightly stronger than dispersion forces.
Opposites attract but not completely hooked like in ionic solids.
H F
H F
Hydrogen bonding
Are the attractive force caused by hydrogen bonded to F, O, or N.
F, O, and N are very electronegative so it is a very strong dipole.
Causes hydrogen to have a large partial positive charge on it
The molecules are small, so they can get close together
The hydrogen partially share with the lone pair of electrons on an atom in a neighboring molecule
The strongest of the intermolecular forces.
Hydrogen Bonding
HH
O+ -
+
H HO+-
+
Hydrogen bonding
HH
O H HO
HH
O
H
H
OH
HO
H
HO HH
O
Hydrogen bonding is the reason why water has unique properties compared to other molecules its same size
Properties: It is a liquid at room temp. It is a good solvent It is less dense as a solid (ice floats)
Just remember Water is not the only molecule that has hydrogen bonds.
Examples:
What type of intermolecular forces do the following molecules have? NH3
O2
CO2
HBr Which of the following compounds
can form dipole-dipole forces: Cl2, CO, NO, CH4
Hydrogen bonding
Dispersion forces
Dispersion forces
Dipole-dipole forces
13.4 Phase Changes
What is a phase? The distinct states of matter when they
are in mixtures How is this different from just states
of matter?
Occur due to changes in temperature.
Phase changes that need energy
Melting
Heat of Fusion
Melting Point
KMT?
Vaporization
Heat of Vaporization
How is this different from evaporation?
KMT?
Boiling Point
Normal Boiling Point
KMT?
Sublimation – Dry Ice Ice in the Freezer
KMT?
Phase Changes that Release Energy
Condensation
What is this the reverse of?
KMT?
Freezing
Freezing Point
How do the melting point & freezing points of a substance compare?
KMT?
Deposition
What is this the reverse of?
KMT?
Heating Curve
Vapor Pressure Graphs
Phase Diagram
For Water
Phase Diagram
For CO2
Video lesson Water, a polar molecule, on YouTube:
http://www.youtube.com/watch?v=DVCYlST6mYQ
ReviewIonic and Covalent Compounds
Practice Quiz and Graphics: http://www.elmhurst.edu/~chm/vchembook/145Areview.html
Internet resources Molecular polarity:
http://www.elmhurst.edu/~chm/vchembook/210polarity.html
Polar covalent compounds: http://www.elmhurst.edu/~chm/vchembook/152Apolar.html
Nonpolar covalent compounds: http://www.elmhurst.edu/~chm/vchembook/150Anpcovalent.html
Ionic compounds: http://www.elmhurst.edu/~chm/vchembook/143Aioniccpds.html
Compare Ionic, Polar, and Nonpolar Bonds: http://www.elmhurst.edu/~chm/vchembook/153Acompare.html
Properties of Molecules
Most have LOW melting & boiling points
tend to be gases and liquids at room temperature
Ex: CO2, NH3, H2O
Polar and Nonpolar molecules have a little bit different properties due to the partial charges.
H - F+ -
H - F
+-H -
F+-
H -
F
+-
H - F +-
H - F+-
H - F
+-
H - F
+-
+-
Properties of Solid Molecules
Two kinds of crystals: Molecular solids – molecules held together
by attractive forces Ex: BI3, Dry Ice, sugar
Network solids- atoms held together by bonds
One big molecule (diamond, graphite) High melting & boiling points, brittle, extremely hard
Graphite Diamond