Solvent Properties


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•  Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water

Water is commonly referred to as the universal solvent due to its capacity to dissolve a large number of substances

Water can dissolve any substance that contains charged particles (ions) or electronegative atoms (polarity)

This occurs because the polar attraction of large quantities of water molecules can sufficiently weaken intramolecular forces (such as ionic bonds) and result in the dissociation of the atoms

The slightly charged regions of the water molecule surround atoms of opposing charge, forming dispersive hydration shells

Solvent Properties of Water

universal solvent

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•  Substances can be hydrophilic or hydrophobic

Substances that freely associate and readily dissolve in water are characterised as hydrophilic (‘water loving’)

  • Hydrophilic substances include all polar molecules and ions

Substances that do not freely associate or dissolve in water are characterised as hydrophobic (‘water-hating’)

  • Hydrophobic substances include large, non-polar molecules (such as fats and oils)

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•  Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in 

   relation to their solubility in water

The transport of essential molecules within the bloodstream will depend on their solubility in water

  • Water soluble substances will usually be able to travel freely in the blood plasma, whereas water insoluble substances cannot

Water Soluble Substances

  • Sodium chloride (NaCl) is an ionic compound and its components (Na+ and Cl) may be freely transported within the blood
  • Oxygen is soluble in water but in low amounts – most oxygen is transported by haemoglobin within red blood cells
  • Glucose contains many hydroxyl groups (–OH) which may associate with water and thus can freely travel within the blood
  • Amino acids will be transported in the blood in an ionized state (either the amine and/or carboxyl groups may be charged)

Water Insoluble Substances

  • Lipids (fats and cholesterol) are non-polar and hydrophobic and hence will not dissolve in water
  • They form complexes with proteins (lipoproteins) in order to move through the bloodstream
  • Hydrophilic portions of proteins, cholesterol and phospholipids will face outwards and shield internal hydrophobic components