• major component of cells 
  • very abundant
  • water is dipolar molecule 
    • made up of 2 hydrogen atoms & 1 oxygen atom
      • oxygen atom has slight negative charge 
      • hydrogen has slight positive charge
    • water has both negative & positive poles 
  • water & hydrogen bonding 
    • positive pole of 1 water molecule attracted to negative pole of other 
      • attractive force - hydrogen bond 
        • relatively weak
          • one tenth strength of covalent bond 
        • huge numbers in water 
          • significant force & responsible for many unusual properties

Properties of Water

  • specific heat capacity 
    • water molecules stick together - hydrogen bonding 
      • takes lots of energy to seperate
      • why water has higher boiling point than predicted 
    • amount of water needed to change 1kg of substance by 1 degrees celcius
    • SHC of pure water = 4190 
  • latent heat of vaporisation
    • amount of energy needed to evaporate 1g of water 
    • when substance changes from liquid to gas - energy required 
    • potential energy stored in forces between molecules need to be


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