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

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Chapter 11: Liquids, Solids, and Intermolecular Forces 11.1 CLIMBING GECKOS AND INTERMOLECULAR FORCES --intermolecular forces: attractive forces that exist between all molecules and atoms -holds many liquids and solids ( i.e. water and ice) together -gecko’s sticky feet micro hairs called setae on toes that branches out to flattened tips called spatulae allows for unsually close contact with surce close contact allows intermolecular forces (significant only at short distances) to hold the gecko to the wall -intermolecular force important for all organisms for many other reasons (i.e. IMF determines shape of protein molecules; imp for structure to DNA) -IMF responsible for the existence of condensed phases state of matter (solid, liq, gas) depends on the magnitude of IMF btwn the constituent particles relative to the amount of thermal energy in the sample -thermal energy: energy associated with the random motion that increases with increasing temperature -thermal energy is high relative to IMF, matter tends to be gaseous - ”””” is low relative to IMF, matter tends to be liq, or solid 11.2 SOLIDS, LIQUIDS, AND GASES: A MOLECULAR COMPARISON -density of solids and liquids > gas -density and molar volume of solid and liq more similar to each other than gas -reason: molecular representation molecules in liq and solid are in close contact with each other while molecules in gas are separated by large distances -low density of gas because of the large separation -notice also that for water: density of solid < liquid atypical behavior -most solids are denser than their corresponding liquids because the molecules move closer together upon freezing -therefore, ice is less dense than liq water because the unique crystal structure of ice results in water molecules moving slightly further apart upon freezing -liquids: even though atoms/molecules are in close contact, thermal energy can partially overcome the attraction btwn them, allowing them to move around one another -for solids, atoms/molecules virtually locked in their positions, only vibrating back and forth about a fixed point
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molecular properties of solids, liquids result in the following macroscopic props: Properties of Liquids Properties of SOlids - high density than gas - indefinite shape and assume shape of their container - definite volume, not easily compressed - high density than gas -definite shape -definite volume, not easily compressed -may be crystalline (ordered) or amorphous (disordered) PHASE DENSITY SHAPE VOLUME STRENGTH OF IM FORCES (relative to thermal energy) Gas Low Indefinite Indefinite Weak Liquid High Indefinite Definite Moderate Solid High Definite Definite Strong EXPLANATIONS: -liq assume container’s shape atoms/moles that compose them are free to flow (move around) -liq not easily compressed atoms/moles are in close contact—cannot be pushed much closer together -gas, in contradst, have great distance btwn them and are easily forced into a smaller volume by increasing external pressure
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This note was uploaded on 05/05/2009 for the course CHEMISTRY CHEM142 taught by Professor Metcalf during the Spring '09 term at UVA.

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

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