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States of Matter Chapter 13
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Matter Let’s get to the heart of it… The particles are in constant motion
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Kinetic-Molecular Theory Describes the motion of individual molecules Kinetic = “to move” Also called Kinetic Theory
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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
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13.2 Forces of Attraction Intermolecular Forces What holds molecules together
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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
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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?
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Dispersion force HH HH HH HH ++ -- HH HH ++ -- ++
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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
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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.
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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
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+ - + - + - + - + - + - + - + - + - + -
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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.
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Hydrogen Bonding H H O ++ -- ++ H H O ++ -- ++
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Hydrogen bonding H H O H H O H H O H H O H H O H H O H H O
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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.
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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
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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.
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Phase changes that need energy Melting Heat of Fusion Melting Point KMT?
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Vaporization Heat of Vaporization How is this different from evaporation? KMT?
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Boiling Point Normal Boiling Point KMT?
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Sublimation – Dry Ice Ice in the Freezer KMT?
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Phase Changes that Release Energy Condensation What is this the reverse of? KMT?
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Freezing Freezing Point How do the melting point & freezing points of a substance compare? KMT?
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Deposition What is this the reverse of? KMT?
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Heating Curve
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Vapor Pressure Graphs
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Phase Diagram For Water
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Phase Diagram For CO 2
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Video lesson Water, a polar molecule, on YouTube: http://www.youtube.com/watch?v= DVCYlST6mYQ http://www.youtube.com/watch?v= DVCYlST6mYQ
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Review Ionic and Covalent Compounds Practice Quiz and Graphics: http://www.elmhurst.edu/~chm/vch embook/145Areview.html http://www.elmhurst.edu/~chm/vch embook/145Areview.html
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Internet resources Molecular polarity: http://www.elmhurst.edu/~chm/vchembook/210pola rity.html http://www.elmhurst.edu/~chm/vchembook/210pola rity.html Polar covalent compounds: http://www.elmhurst.edu/~chm/vchembook/152Apo lar.html http://www.elmhurst.edu/~chm/vchembook/152Apo lar.html Nonpolar covalent compounds: http://www.elmhurst.edu/~chm/vchembook/150Anp covalent.html http://www.elmhurst.edu/~chm/vchembook/150Anp covalent.html Ionic compounds: http://www.elmhurst.edu/~chm/vchembook/143Aio niccpds.html http://www.elmhurst.edu/~chm/vchembook/143Aio niccpds.html Compare Ionic, Polar, and Nonpolar Bonds: http://www.elmhurst.edu/~chm/vchembook/153Aco mpare.html http://www.elmhurst.edu/~chm/vchembook/153Aco mpare.html
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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.
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H - F ++-- ++ -- ++ -- ++ -- ++ -- ++ -- ++ -- ++ -- + -
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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
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Graphite Diamond
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