Zusammenfassung der Ressource
2.4 Water and it's Functions
- The Dipolar water
molecule
- A water molecule is made up of one Oxygen atom, and two hydrogen atoms
- oxygen has slightly negative charge, hydrogen has a slightly positive charge
- This means a water molecule has both negative and positive poles = dipolar
- Hydrogen Bonding
- Different poles attract
- Positive pole of one H2O
Molecule is attracted to
negative pole of another water
molecule
- This is a hydrogen bond
- Although each H bond is fairly weak, together they
form important forces that cause the water
molecules to stick together
- These bonds give water its unusual properties
- Specific Heat Capacity of Water
- Hydrogen bonds between water molecules can absorb a lot of energy
- Water has a high specific heat capacity
- this means it takes a lot of energy to heat it up
- So water doesnt experience rapid temperature changes
- This means it is a good habitat, as the
temperature underwater would be more
stable
- It also means the water inside organisms is a
fairly stable temperature - helping them to
maintain a constant internal body temperature
- Latent Heat of Vaporisation of Water
- Water has high latent heat of vaporisation
- takes a lot of energy to break the H bonds between H2O molecules
- a lot of energy is used up to evaporate water
- Effective means of cooling when sweating as body heat is used to evaporate the water
- Cohesion and Surface tension
- Cohesion - the attraction between molecules of the same type
- H2O molecules are very cohesive (tend
to stick together) because they're polar
- Strong cohesion helps water flow = great for transporting substances
- E.g/ Its how water travels in columns up the xylem in plants
- Strong cohesion = water has high surface tension when it comes into contact with air
- This is the reason why sweat --> droplets
- Reason why pond skaters and some other
insects can 'walk' on the surface of a pond
- Water is an important METABOLITE
- Produced in condensation reactions
- forming a new bond
- Used in hydrolysis reactions
- breaking a bond
- Water as a solvent
- dissolves gases e.g/ O2 and CO2
- dissolves wastes e.g NH3
- disolves inorganic ions and small hydrophilic molecules
e.g/ Amino acids, monosaccharides and ATP
- dissolves enzymes, whose reactions take place in solution