water

• cohesion is the tendency for water molecules to form hydrogen bonds with other water molecules
• surface tension demonstrates cohesion
• adhesion is the tendency for water molecules to form hydrogen bonds with other molecules that are charged or polar
• water acts a metabolite (used to break down many complex molecules by hydrolysis) and is the medium in which all metabolic reactions take place in cells
• different poles attract meaning that the positive pole of one water molecule is attracted to the negative pole of another water molecule -> this attractive force is called a hydrogen bond
• water molecules are described as dipolar despite having no overall charge as the oxygen atom has a slight negative charge and the hydrogen atoms have a slight positive charge
• because water molecules bond to each other, it takes more energy to separate them therefore water has a high boiling point
• It therefore takes more energy to heat a given mass of water giving water a high specific heat capacity
• water's high specific capacity means it acts as an important buffer against sudden temperature changes (this means that the aquatic environment is a stable one)
• as organisms are mostly water, water also buffers them against sudden temp changes
• the hydrogen bonds between water molecules means that it takes a lot of energy to evaporate 1 gram of water (this energy is called latent heat of vapourisation)
• Evaporation of water through sweat in mammals is a very effective means of cooling as body heat is used to evaporate water
• cohesion allows water to be pulled up through a tube such as the xylem vessel
• water readily dissolves other substances
• water can dissolve: gases (oxygen + CO2), wastes (urea and ammonia), inorganic ions (monnosaccahrides, ATP and amino acids) and enzymes (reactions take place in solution)