3 phases - dependent on the intermolecular forces
- gas
- takes on volume/shape of container
- compressible
- flows easily
- diffusion occurs rapidly
- liquid
- takes on shape of container
- doesn’t expand to fill container
- incompressible
- flows readily
- diffusion occurs slowly
- solid
- keeps its own shape/volume
- incompressible
- doesn’t flow
- diffusion occurs very slowly
intermolecular forces - much weaker than ionic/covalent bonds
- molecules remain intact when intermolecular forces broken
- stronger intermolecular forces >> higher melting/boiling points
- van der Waals forces - intermolecular attractive forces between neutral molecules
- dipole-dipole, London dispersion, hydrogen bonding
- ion-dipole force - between ion and partial charge on an end of polar molecular
- ion charge increase or dipole moment magnitude increase >> increase in magnitude of attraction
- important for solutions of ionic substances in polar liquids
- dipole-dipole force - attraction between positive/negative ends of neutral polar molecules
- only effective when polar molecules very close together
- increasing polarity >> increasing intermolecular attractions
- smaller molecules >> increasing attraction
- London dispersion force - instantaneous dipole moment
- found between nonpolar and polar molecules
- due to temporary dipole moments at particular moments
- polarizability - how easily an electric field can change the molecule’s charge distribution
- increasing molecular weight >> increasing strength of dispersion forces
- most massive/polar molecules have largest attraction forces
- hydrogen bonding force - intermolecular attraction between hydrogen atom in polar bond and unshared electron pair on another molecule
- generally stronger than dipole-dipole/dispersion forces
- hydrogen’s small size lets it get close to electronegative atom
- equal amounts of water take up more volume as solid than as liquid (usually reversed for other substances)
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