Physical propierties of alkanes

  • Interaction by London forces: In alkanes, the melting points increase with increasing molecular size, a larger surface area produces a greater attraction due to London forces.
  • Boiling points also increase with molecular weight, the heavier a molecule is, the more energy it requires to go from the liquid to the gaseous state.
  • Branched alkanes have smaller surface areas than their linear isomers, so the attractive forces are lower, leading to lower melting and boiling points.
  • Alkanes are insoluble in water due to their almost zero polarity. Their densities are between 0.6 and 0.8 g/ml, so they float in water.