Chapter 11 - Intermolecular Forces, Liquids, and Solids

Chapter 11 - Intermolecular Forces, Liquids, and Solids -...

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GENERAL CHEMISTRY CHAPTER 11 – INTERMOLECULAR FORCES, LIQUIDS, & SOLIDS PAGE 1 OF 22 Intermolecular Forces, Liquids and Solids Recall: Matter can be classified as solid, liquid, or gas based on the characteristics it exhibits State Shape Volume Compress Flow Solid Fixed Fixed No No Liquid Indefinite Fixed No Yes Gas Indefinite Indefinite Yes Yes Fixed = keeps shape when placed in a container Indefinite = takes the shape of the container The molecules in a gas have complete freedom of motion Their kinetic energy overcomes the attractive forces between the molecules The molecules in a solid are locked in place, they cannot move around T hough they do vibrate, they don’t have enough kinetic energy to overcome the attractive forces The molecules in a liquid have limited freedom – they can move around a little within the structure of the liquid They have enough kinetic energy to overcome some of the attractive forces, but not enough to escape each other The properties of solids, liquids, and gases can be explained based on the kinetic energy of the molecules and the attractive forces between molecules Kinetic energy tries to give molecules freedom of motion Attractive forces try to keep the molecules together One phase of matter can be transformed to another by changing the temperature, pressure, or both Intermolecular Forces Intermolecular forces = the forces that act between molecules rather than within an individual molecule In gases, the forces are negligible and gas molecules act independent of one another In liquids/solids, intermolecular forces are strong enough to hold the molecules in close contact The stronger the intermolecular forces, the more difficult it is to separate molecules These forces result in higher melting and boiling points of a substance
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GENERAL CHEMISTRY CHAPTER 11 – INTERMOLECULAR FORCES, LIQUIDS, & SOLIDS PAGE 2 OF 22 Polar Forces of Attraction A dipole-dipole force is when the (+) and (-) ends of different molecules are attracted to one another Positive end polar molecule to negative end polar molecule Polar molecules always have a permanent dipoole Ion-dipole forces = result of electrical interactions between an ion and the partial charges on a polar molecule The strength of the ion-dipole attraction is one of the main factors that determines the solubility of ionic compounds in water The larger the charge the stronger the attraction The longer the distance the weaker the attraction However, these attractive forces are small relative to the bonding forces between atoms What affect do these forces have? Raises the boiling and melting points relative to non-polar molecules of similar size and shape The higher the normal boiling point of the liquid, the stronger the intermolecular attractive forces
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GENERAL CHEMISTRY CHAPTER 11 – INTERMOLECULAR FORCES, LIQUIDS, & SOLIDS PAGE 3 OF 22 London Dispersion Forces/van der waals forces
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This note was uploaded on 01/21/2011 for the course PHYS 4A 60865 taught by Professor L. oldewurtel during the Fall '09 term at Irvine Valley College.

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Chapter 11 - Intermolecular Forces, Liquids, and Solids -...

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