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Condensed States of Matter


    1.    Explain how the kinetic-molecular theory accounts for the physical properties of solids and liquids.

    2.    Describe the different types of intermolecular forces and explain how the influence the properties of liquids and solids.



Notes: (14-1)

Although the Kinetic-Molecular theory was used primarily to explain the actvity and properties of gases, it can also be used to describe the condensed states of solids and liquids.

1st look at the properties of different phases of matter.

(people.uis.edu/gtram1/MaterialsScience/ CH-1-2000/img002.GIF)

According to the Kinetic-Molecular theory, the state of a substance depends on the attractive forces between the molecules of the substance.  There are three basic types.

solids have the strongest intermolecular forces & gases the weakest

Intermolecular Forces

1)  Intramolecular forces

ionic bonds (between metals and non-metals) - involves the transfer on electrons - generally solids
covalent bonds (between two non-metals) - involves the sharing of electrons - liquids / solids / gases - the phase depends on how strongly the individual molecules attract each other

Both ionic and covalent bonds are formed in an attempt to satisfy the noble gas (octet) rule of 8 valence electrons in the outermost energy shell.

2)  Intermolecular Dispersion Forces (dipole forces)

Temporary forces created by the rearrangement of the electrically negative and flexible electron cloud around the rigid and positive nucleus
measured by the boiling point of an atom or molecule - point where the kinetic energy becomes greater than the intermolecular forces


(web.mse.uiuc.edu/.../Notes/slides/ bonding/vanderwaals.gif)

        Induced Dipole Forces:

temporary force caused by the rearrangement of electron cloud densities
Very weak 

        Dipole-Dipole Forces:

Created by polar (covalently bonded) molecules that have distinct positive and negative ends (water)
Strength determines the phase of the substance
Diatomic molecules set up permanent dipoles
Polyatomic molecules set up dipoles based on their geometric shapes
Signified by the Greek letter delta (d)

interactions between polar molecules(www.chem.unsw.edu.au/.../hainesIMF/ images/dipoledipole.jpg)


Hydrogen Bonding

Force created between the least electronegative atom (hydrogen) and the most electronegative atoms (fluorine, oxygen, and nitrogen)
reason some substances stay as liquids even though their other forces are less than their kinetic energy

(faculty.stcc.edu/dickerman/P_Bio_I/ hydrogen%20bonds.gif)















Last modified: March 10, 2003