Chapter 10 - 1 KINETIC THEORY OF MATTER - molecules in...

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1 KINETIC THEORY OF MATTER - molecules in matter are always in motion - speed of molecules is proportional to the temperature THE STATES OF MATTER 1. Gas a) ideal gas - molecules move freely - molecules have no interactions with each other - no attraction or repulsion - like ping-pong balls b) real gas - molecules move freely - molecules have small attractions for each other - like “sticky” ping-pong balls 2. Liquid - molecules move but movement is heavily influenced by other molecules - molecules must move through a crowd of molecule 3. Solid - molecules vibrate about fixed position in crystal lattice - motion is not great enough to overcome attractions - molecules stay in a specific arrangement CHARGE DISTRIBUTIONS OF MATTER 1. Ion 2. Dipole - A polar molecule has a dipole. - The value of a dipole depends on a) polarity of bonds b) molecular geometry 3. Induced Dipole - A molecule can have its electron cloud polarized by neighboring charge. - Consider F 2 . - Fluorine molecule has no dipole. F F F F O H H H C N
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2 - Consider F 2 next to sodium ion, Na + . - Negative electron cloud adjusts to move closer to positive ion. - Fluorine molecule now has a dipole! - Sodium ion induces dipole in fluorine. - Thus fluorine has an induced dipole . Some atoms in molecules have electron clouds that adjust easier than others. - Sodium ion induces larger dipole in iodine molecule than in fluorine. The ability of an atom or molecule to adjust its electron cloud in response to an outside charge is called its polarizability . The less tightly bound to the nucleus the electrons are, the more polarizable they are. - as a periodic trends, polarizability increases as row increases. Example: Arrange the following atoms in order of increasing polarizability: Ar, He, Kr, Ne and Xe. Answer: He, Ne, Ar, Kr, Xe Xe – very polarizable He – barely polarizable Na + F F δ - δ + Na + F F Na + I I
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INTERMOLECULAR FORCES Overriding Principles 1. Opposite charges attract. 2. The greater the charge, the greater the attraction. Types of Intermolecular Forces 1. Ion – Dipole Example: salt water - strongest type of intermolecular force - as the charge increases, the strength of the force increases Ca 2+ --- H 2 O forces are stronger than Na + --- H 2 O forces 2. Dipole – Dipole Example: Formaldehyde Molecules with greater dipole moments have greater attractions to each other. + O
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This note was uploaded on 09/27/2010 for the course CHEM 220 taught by Professor Bates during the Spring '10 term at Skyline College.

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Chapter 10 - 1 KINETIC THEORY OF MATTER - molecules in...

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