liquids - properties explained by intermolecular forces

• viscosity - resistance of a liquid to flow
  • measured by timing to see how long it takes an amount of liquid to flow through a tube
  • poise (P) - unit of viscosity, g/cm-s
  • lower temperature, larger molecular weight >> lower viscosity
• surface tension - energy needed to increase surface area by a certain amount
  • cohesion - forces that bind similar molecules to each other
  • adhesion - forces that bind substance to a surface
• capillary action - rise of liquids up narrow tubes
  • used by plants to move water/nutrients upwards
  • adhesion between liquid and tube increases surface area

solid structures - either crystalline or noncrystalline (amorphous)

• crystalline solid - molecules arranged in well-defined arrangements
  • have flat surfaces, definite angles, regular shapes
  • brings particles in closest contact >> maximizes attractive forces
  • unit cells - repeating unit of a crystalline solid
  • crystal lattice - 3D array of points representing the crystal
  • primitive cubic - unit cell where lattice points at corners only
  • centered cubic - additional lattice point at center of cell
  • face-centered cubic - additional lattice points at center of each face
• packing of spheres - each sphere surrounded by 6 others in each layer
  • spheres rest in depressions of surrounding layers
  • hexagonal close packing - 3rd layer repeats the 1st, 4th layer repeats the 2nd
  • cubic close packing - 4th layer repeats the 1st
  • coordination number - number of particles immediately surrounding 1 particle on all sides
• amorphous solid - no orderly structure, usually made of large complicated substances

bonding in solids - arrangement of particles determines melting point, hardness, etc

• molecular solids - have molecules/atoms held together by intermolecular forces
  • soft, low melting points
• covalent-network solids - atoms held together in large networks by covalent bonds
  • much stronger than molecular solids, w/ higher melting points
• ionic solids - ions held together by ionic bonds
  • strength depends on charges of ions
  • charges/relative sizes determine structure of solid
• metallic solids - made entirely of metal atoms
  • each atom has 8 or 12 surrounding atoms
  • valence electrons delocalized throughout entire solid
  • mobility of electrons promotes conductivity