water Flashcards
how do hydrogen bonds form between water molecules
water is polar: O is more electronegative than H so attracts electrons in covalent bonds more strongly
forms O δ- and H δ+d
there are intermolecular forces of attraction between a lone pair of O of one molecules and H on an adjacent molecule
state the 7 biologically important properties of water
habitat for aquatic animlals
high surface tension
incompressible
solvent for chemical reaxtions in the body
high specific heat capacity
high latent heat of vaporisation
cohesion between molecules
why is the incompressible nature of water important for organisms
provides turgidity to plant cells
provides hydrostatic skeleton for some small animals e.g. earthworms
explain why ice floats on water and why is this important for organisms
ice is less dense than water because H-bonds hold molecules in fixed positions further away from each other
insulates, water in artic climates so aquatic organisms can survive
water acts as a habitat
why is the high surface tension of water important for organisms
slows water loss due to transpiration in plants
some insects can ‘skim’ across the surface of water
why is water an important solvent for organisms
polar universal solvent dissolves and transports charged particles involved in intra and extracellular reactions
e.g PO43- for DNA synthesis
allows chemical reactions to occur within cells (as the dissolved solutes are more chemically reactive when they are free to move about)
why are the high specific heat capacity of water important for organisms
SHC = the amount of thermal energy required to raise the temperature of 1kg of that substance by 1 degree
high SHC is due to the many H-bonds present in water
it takes a lot of thermal energy to break these bonds and a lot of energy to build them
this means the temperature of water doesn not flucate greatly - maintains a constant temperature
provides a stable habitat in aquatic environments such as lakes and the ocean
acts as a temperature buffer which enables endotherms to resist fluctuations in core temperature to maintain optimum enzyme activity
why is the high latent heat of vaporisation of water important for organisms
in order to change state (from L to G) a large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate
only a little water is required to evaporate for the organism to lose a great amount of heat
provides a cooling effect from living organisms - transpiration from leaves or evaporation of water in sweat on the skin
why is cohesion and adhesion of water important for organisms
H-bonds between water molecules allows for strong cohesion between water molecules
allows columns of water to move through the xylem of plants and through blood vessels in animals
enables surface tension where a body of water meets the air
water is able to hydrogen bond to other molecules, such as cellulose = adhesion
enables water to move up the xylem due to transpiration
