2.2 water

electronegativity

electronegativity

the affinity for electrons

water: O has higher EN than H → more -ve O, more +ve H → partial charges → polar

bonding in water molecules

intramolecular: strong covalent bonds

intermolecular: weaker H bonds, but many so stronger

can form H bonds w other polar molecules

properties of water: cohesion & adhesion

cohesion: bw water

adhesion: water + other polar molecule

eg. capillary action — both: cohesion bw water molecules to transport against gravity, not separated by suction forces. adhesion bw water & xylem walls.

properties of water: thermal properties

high shc: amt of heat req to increase by 1C. why? ability to form H bonds — heat req to break bonds/heat released to build bonds.

high latent heat of vaporisation: amt of heat req to evaporate — prod a cooling effect w minimal loss of water.

eg. sweat in mammals — principal component is water. hypothalamus. cools the skin & blood flowing through the skin as heat is taken from tissues.

eg. transpiration in plants

eg. dogs panting

properties of water: solvent properties

h2o is a polar molecule — form hydration shells

forms h bonds w polar molecules → both dissolve.

signif: h2o is an excellent solvent for polar molecules

eg. cytoplasm

transport of substances in blood

blood plasma: glucose, amino acids, sodium chloride (all polar)

hemoglobin: oxygen (non polar)

lipoprotein complexes: fats & cholesterol — proteins embedded in phospholipid layer

methane vs h2o thermal properties

opposites in these categories: polar, can form H bonds, takes a lot of en to break H bonds & change temp + state, has higher SHC + heat of vaporisation.