·         water is a very important biological molecule – it is found in large percentages in all living forms

·         it is a polar covalent molecule, where the two hydrogens bond with the central oxygen, creating an angle of 104.5 

·         this shape gives water its polar nature

·         the polar nature of water causes intermolecular bonds

·         water is considered a universal solvent – more substances dissolve in water than in any other substance

·         the reason for this is because of its unique polarity – it has partial positive and partial negative to provide attachment with other molecules 

·         all ionic substances dissolve in water and any polar covalent substance dissolves in water

·         this is because “like dissolves like”, meaning polar substances are miscible in other polar substances, and non-polar substances are miscible in other non-polar substances

·         for example, water and oil don’t mix, because water is polar and oil is non-polar

·         thus water and oil are immiscible

·         water and vinegar mix because both are polar substances

·         oxygen does not dissolve in water that well (or blood, since blood is mostly water)

·         that is why hemoglobin (a carrier molecule of oxygen) is necessary in blood – it increases the amount of O2 that can dissolve in blood

·         large, non-polar molecules, such as fats and oils are considered hydrophobic (meaning “water-fearing”) since they cannot form hydrogen bonds with water

·         polar molecules are hydrophilic (meaning “water-liking”) since they can form hydrogen bonds with water

·         molecules that contain both hydrophobic and hydrophilic parts are called amphophilic molecules