Understand the importance of water as a solvent in transport, including its dipole nature

  • Water is a polar molecule= it has an unevenly distributed chemical charge
    • The two hydrogens are pushed towards each other forming a V shaped molecule
    • Hydrogen= slightly positive charge
    • Oxygen= slightly negative charge (electrons are more concentrated at this end)
  • Positively charged end of water molecule is attracted to the negative ends of surrounding molecules
  • Hydrogen bonding:
    • Holds the water molecules together
    • Results in water being liquid at room temperature


  • Chemicals easily dissolve in water= biochemical reactions can occur in cytoplasm of cells
  • Dissolved substances can be transported around organisms
    • in animals via the blood and lymph systems
    • in plants via the xylem and phloem
  • Polar molecules dissolve easily in water molecules
  • Polar groups g. –OH become surrounded by water and go into solution
  • Polar substances= hydrophilic= water attracting
  • Hydrophobic= non-polar, g. lipids do not dissolve in water> allows transport in blood
  • A large amount of energy needed to break hydrogen bonds in water
    • a large input of energy causes only a small increase in temperature= water warms up and cools down slowly