Chapter_13_Notes - Chapter 13: LIQUIDS [13-1]...

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Chapter 13: LIQUIDS [13-1] Kinetic-Molecular Description of Liquids and Solids *Table 13-1* compares the properties of solids, liquids, and gases Both liquids AND gases are fluids… they flow easily Liquids DIFFUSE into other liquids with which they are miscible o Miscible liquids are soluble in one another Water dissolves in alcohol Gasoline dissolves in motor oil o Immiscible liquids are insoluble in one another Water does not dissolve in cyclohexane Water does not dissolve in oil Cooling a liquid causes its molecules to slow down If temperature is reduced enough, solidification occurs o Strong, short-range attractive interactions between molecules overcome the reduced kinetic energy of the molecules In comparing the degree of ordering of particles in solids, liquids and gases, we find: o Least ordered [gas<liquid<solid] most ordered What about two molecules attracting each other? There are 4 types of intermolecular forces o Ion-ion interactions: attract each other b/c of opposite charge o Hydrogen bonding: o Dipole-dipole interactions: similar to ion/ion o London dispersion forces: aka dispersion forces or London forces o Relative strength: London<dipole<h-bonding<ion-ion interactions o Intra stronger than any of the inter forces Ion-ion interactions: o Interactions between two oppositely charges ions(fully charged ions. .ex: +1, +2 or -1 -3) o Governed by coulomb’s lay F is proportional to (q+)(q-)/(d^2) Q+ and q- are the ion charges, d is the distance b/t the ions Remember that we are no longer talking about a single NaCl molecule!! Ionic solids for crystal lattices! [13-2] intermolecular attraction and phase changes The value of F in Coulomb’s law tells us the energy of attraction between two oppositely charged ions o “gotta make em jiggle” o If the energy of attraction is large , then it is difficult to separate the ions This results in higher melting points and boiling points
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It also means that the substance is not very soluble in water o If the energy of attraction is small . Then it is easier to separate the ions The melting and boiling points are lower The substance is more soluble in water. o Higher the oxidation state of the cation the smaller it is Anions get bigger as you add electrons o Ex 13-1: arrange in increasing melting/boiling NaF<CaF2<CaO Dipole-dipole interactions: a dipole is created when two opposite charges are separated by dome distance, d (partially charged ions) o Dipole moment= IqI x d o Is a vector quantity o Two large charges close together=two small charges far apart o Remember that the electron pair(s) in heteronuclear covalent bonds are not equally shared o A dipole is created, based on relative electro-negativities of the atoms involved in the
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This note was uploaded on 07/31/2008 for the course BIOL 1103 taught by Professor Armstrong during the Spring '07 term at University of Georgia Athens.

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Chapter_13_Notes - Chapter 13: LIQUIDS [13-1]...

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