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Evaporation

• Evaporation occurs when a liquid absorbs heat energy from its surroundings and energises some of the liquid molecules up to a point where the internal bonding energies between molecules are overcome and is able to escape the liquid to form a vapour.
  
  The independent vapour molecules can also loose energies to the surroundings and on collision with similar molecules, bond and reform into the liquid phase.
  
  In a closed, isolated liquid/vapor situation, at a steady temperature, the vapour phase will become supersaturated and a stable equilibrium situation is established, with no increase in the vapour concentration or a decrease in the liquid volume.
  
  That is no more (increase in) evaporation .
  
  Conversely if the vapor phase is constantly removed by air movement a greater capacity for evaporation is established.
  
  
• Evaporation from a mixture of liquids sees the mixture become more concentrated in the less volatile substance, with time, due to the higher evaporation rate of the more volatile liquid.
  
  This will occur up to a point where the altered concentration ratios of the liquids involved, changes the interaction dynamics between the molecules (see distillation theory).