water Flashcards
how much of the cells content is made up of water
80%
how is water a solvent
some substances dissolve in it
- most metabolic reactions take place in solution e.g in the cytoplasm so water becomes very important
how does water help with temperature control
due to the high latent heat of vapourisation and high specific heat capacity
how is water cohesive
water molecules are very cohesive (they stick together) which helps water transport in plants
what is the structure of a water molecule
one oxygen atom joined to two hydrogen atoms by shared electrons
why is a slight positive charge left on the outer side of the hydrogen atoms
because the shared negative hydrogen electons are pulled toward the oxygen atom, the other side of each hydrogen atom is left with a slight negative charge
what do the unshared negative electrons on the oxygen atom give
a slight negative charge
how is water a polar molecule
one side is negatively charged and the other is positive
what is hydrogen bonding in water
- the slightly negatively charged oxygen atoms attract the slightly positive charged hydrogen atoms of other water molecules
- this attraction is called hydrogen bonding and it gives water some of its useful properties
what is hydrolysis
requires water to break a bond
what is condensation reaction
releases water to form a bond
water has a high latent heat of vaporisation -what does this mean?
- it takes alot of energy (heat) to break the hydrogen bonds between water molecules
- so water has a high latent heat of vaporisation- a lot of energy is used up when water evaporates
- This is useful for living organisms because it means they can use water loss through evaporation to cool down without losing too much water ( e.g. humans sweat to release heat)
how can water buffer changes in temperature
- the hydrogen bonds between water molecules can absorb alot of energy
- so water has a high specific heat capacity- it takes alot of energy to heat it up
- this is useful for living organisms as water doesnt experience rapid temp changes
- water inside organisms maintains a fairly constant temp
- helps maintain a constant internal body temp
how does water work as a solvent
the molecule can be surrounded by either the positive or negative end of the water molecule meaning both positive and negative molecules can be dissolved when surrounded by water
theres a strong cohesion between molecules.. how does this work
- cohesion is the attraction between molecules of the same type, water molecules have strong cohesion because they are polar
what does cohesion do to waters ability to flow
cohesion makes water more able tof low making it great for transporting substances (for example water travelling up the xylem)
what does cohesion do in relation to surface tension
strong cohesion means water has high surface tension when it comes into contact with air
- this is why sweat droplets form cooling organisms down
