water Flashcards
is water a dipolar molecule?
yes
- has two differently charged regions
why does water have an unevenly distributed charge
- oxygen atom is slightly negative
- hydrogen atoms are slightly positive
where do the hydrogen bonds form in water?
between the oxygen and hydrogen atom
what are the five key properties of water?
- it is a metabolite
- important solvent in reactions
- high heat capacity
- large latent heat of vapourisation
- strong cohesion between water molecules
what reactions is water involved in? (water as a metabolite)
- photosynthesis
- hydrolysis reactions
- condensation reactions
water as a solvent
- can dissolve many substances
- positive charge on H+ ions attracts negative ions solutes
- negative charge on O- attracts positive ion solutes
why cant lipids/ some other molecules dissolve in water
- because they are non polar
- are not attracted to charged oxygen/hydrogen molecules
- are therefore hydrophobic
why is it useful that water is a universal solvent?
enables polar substances to be easily transported around animals and plants
e.g. in blood or xylem
what does high specific heat capacity mean?
- a lot of energy is required to raise temperature of water
- ( because energy is required to break hydrogen bonds between water molecules)
why is high specific heat capacity useful?
- buffers changes in temperature
- temperature of water will remain relatively stable (even if surrounding temp changes)
- therefore internal temperatures of plants and animals stays constant (large proportion of organism is water)
- ezymes do not denature or reduce in activity (aquatic organisms)
what does large latent heat of vapourisation mean?
- a lot of energy is required to convert water in its liquid state to a gaseous state
- ( because energy is required to break hydrogen bonds between water molecules)
why is a large latent heat of vapourisation advantageous?
- water provides cooling effect
- when humans sweat they release water onto skin
- heat energy from skin is transferred to water to evapourate it , therefore remoing heat + cooling organism
how is large latent heat useful in plants?
- plants release water during transpiration
- provides cooling effect for plants
strong cohesion of water
- water molecules sticking together
- due to hydrogen bonds
why is the strong cohesion of water advantageous?
- when water moves up xylem (transpiration), it moves in continous column of water
- advantageous because its easier to draw up column rather than individual molecules
- ALSO, provides surface tension to water
- advantageous because it enables small invertebrates to move and live on the surface/provides habitat away from predators in water
