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