Chapter 11 - Liquids and Intermolecular 

  • Intermolecular - Forces between molecules.
  • ==Boiling== breaks intermolecular forces.
Properties that reflect intermolecular forces
  • Boiling point
  • Melting point
  • Viscosity
  • Surface tension
  • Capillary action
  • Water has a ==high surface tension==.
States of matter
  • Gas
  • Liquid
  • Solid   * ==Gases and liquids== are called fluids.   * ==Liquids and solids== are called condensed states, they have strong forces.
Intermolecular forces (Weakest to strongest)
  • Dispersion forces or London forces - Only occurs in non-polar molecules. It is constantly shifting to a different set of temporary forces.   * The tighter the molecules, the lower the surface area they have, and the lower their boiling point is.     * Ex. Neopentane has a ==lower boiling point== than pentane because neopentane has a lower surface area.
  • Dipole-dipole interactions - They form permanent dipoles. Occurs in polar molecules.   * Bad interactions - 2 positive or 2 negative banging into each other.
  • Hydrogen bonding - Strongest force. It can only be formed with a hydrogen atom bonding with a nitrogen, oxygen, or fluorine atom.
  • Crystalatus - Smallest defined unit that repeats inside a molecule.
  • Water is the only liquid that freezes from the top.
Ion-dipole interactions
  • Found in solutions of ions.
  • Can only occur with polar compounds.
Relative strengths of intermolecular forces
  • When 2 molecules have comparable moral masses and shapes, dispersion forces are equal.
  • When 2 molecules have very different molar masses and there's no H-bonding, dispersion force determines the substance with stronger attractions.
Properties affected by intermolecular forces
  • Viscosity - Resistance of a liquid to flow. Increases with strong forces, decreases with higher temperature.
  • Surface tension - Water acts as if it has a skin be of the extra forces on the surface allowing water to bead up when in contact with nonpolar surfaces.
  • Capillary action - The rise of liquid up narrow tubes.   * Cohesive forces - Intermolecular forces that bind similar molecules to one another.   * Adhesive forces - Intermolecular forces that bind a substance to a surface.
Phase changes
  • Phase change - Conversion from one state to matter to another.   * Melting / Fusion - Solid to liquid, endothermic.   * Freezing - Liquid to solid, exothermic.   * Vaporization - Liquid to gas, endothermic.   * Condensation - Gas to liquid, exothermic.   * Sublimation - Solid to gas, endothermic.   * Deposition - Gas to solid, exothermic.
Heating Curves
  • Heating curve - Graph of temperature (y) and the heat added (x).
Vapor pressure
  1. As temperature increases, more molecules are able to have enough energy to become a gas.
  • P = nRT/V
  • P = MRT   * M - molarity   * R - gas constant
  • Vapor pressure - How much of a liquid evaporates at a certain pressure.
  • At any temperature, some liquid molecules have enough energy to escape the surface and become a gas.
Vapor pressure curves
  • Natural log of the vapor pressure - It’s inversely proportional to its temperature.

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  • Clausius-Clayperon equation   * We can find ΔH of vaporization if we know the vapor pressure and the temperature at one point.   * We can find the pressure at point 1 when we know the ΔH of vaporization and the temperature at point 2.
  • Formula simplification
Phase diagrams
  • Phase diagram - A graph that shows the states of matter under conditions of temperature and pressure.
  • Triple point - The point where all three states of matter coexist.
  • Critical point - The point at which no amount of pressure alone can liquify the gas.   * Here you can’t tell the difference between a gas and a liquid.
  • PHASE DIAGRAM OF WATER
  • Water can melt only by pressure.
  • The slope of the melting curve is negative, meaning that as the pressure goes up, the melting point goes down.
  • CARBON PHASE DIAGRAM
  • Carbon has two triple points.   * Triple points are always between the liquid and gas or between two solids.

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