• Crystal structure
• close together and ~ same distance
• proven through xray diffraction
• Structures
  • Crystalline
    • hard
  • Polycrystalline
    • plastics
    • aren't hard and brittle
  • Amorphous
    • Rubbers
    • no definite structure
• Density
  • How much matter in a volume
  • $$Density = \frac{Mass}{Volume}$$
  • same density regardless of colume
• Elasticity
  • change in size or shape when subjected to external forces
  • Like rubber band
  • if it returns to its original shape it is Elastic if not then it is Inelastic
  • Hooks Law
    • stretch is proportional to force
    • only applies within elastic limit (spring can't stretch forever etc.)