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 (20 o C-25 o C, 68 o F-77 o F) all particles of matter have the same kinetic energykinetic 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 Forces What 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  F 2 is a gas  Br 2 is a liquid  I 2 is a solid All are nonpolar but why are they different states of matter?

Dispersion force HH HH HH HH ++ -- HH HH ++ -- ++ 

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. HFHF  HFHF 

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 H H O ++ -- ++ H H O ++ -- ++

Hydrogen bonding H H O H H O H H O H H O H H O H H O H H 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? NH 3 O 2 CO 2 HBr  Which of the following compounds can form dipole-dipole forces: Cl 2, CO, NO, CH 4 Hydrogen bonding 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 CO 2

Video lesson  Water, a polar molecule, on YouTube: DVCYlST6mYQ DVCYlST6mYQ

Review Ionic and Covalent Compounds  Practice Quiz and Graphics: embook/145Areview.html embook/145Areview.html

Internet resources  Molecular polarity: rity.html rity.html  Polar covalent compounds: lar.html lar.html  Nonpolar covalent compounds: covalent.html covalent.html  Ionic compounds: niccpds.html niccpds.html  Compare Ionic, Polar, and Nonpolar Bonds: mpare.html mpare.html

Properties of Molecules  Most have LOW melting & boiling points  tend to be gases and liquids at room temperature  Ex: CO 2, NH 3, H 2 O  Polar and Nonpolar molecules have a little bit different properties due to the partial charges.

H - F ++-- ++ -- ++ -- ++ -- ++ -- ++ -- ++ -- ++ -- + -

Properties of Solid Molecules  Two kinds of crystals: Molecular solids – molecules held together by attractive forces  Ex: BI 3, Dry Ice, sugar Network solids- atoms held together by bonds  One big molecule (diamond, graphite)  High melting & boiling points, brittle, extremely hard

Graphite Diamond