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4973709
2.4 Water and it's Functions
Description
AS - Level Biology (2 - Nucleic Acids) Mind Map on 2.4 Water and it's Functions, created by Bee Brittain on 29/03/2016.
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water
biology
aqa
a-level
as-level
science
cohesion
surface tension
water as a solvent
properties of water
latent heat of vapourisation
specific heat capacity of water
dipolar water molecule
hydrogen bonding in water
hydrogen bonding
biology
2 - nucleic acids
as - level
Mind Map by
Bee Brittain
, updated more than 1 year ago
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Bee Brittain
over 8 years ago
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Resource summary
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
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