Mind Map by Jackj888, updated more than 1 year ago
Created by Jackj888 about 7 years ago


Biology (Topic 1: Lifestyle, Health and Risk) Mind Map on WATER, created by Jackj888 on 04/14/2013.

Resource summary

1.1 Each water molecule is slightly polarised,
1.1.1 This means that there is an ever so slightly negative part, the oxygen atom, and an ever so slightly positive part, the hydrogen atoms The separation of this charge is called a dipole. The charges are represented as δ+ or δ-
1.1.2 The most important result of this charge separation is that water molecules will form hydrogen bonds. This is caused by a weak electrostatic attraction between the negative oxygen atom of one molecule and the positive hydrogen atoms of another molecule This means the molecules of water stick together more than you would expect as although hydrogen bonds are weak, there are a great amount of them. Due to this water has high melting and boiling points, as it takes more energy to break the attractive force of all the hydrogen bonds. This also explains waters relatively high points in comparison to molecules of a similar size. Water has a high specific heat capacity.
2.1 Water is an unusual and excellent solvent
2.1.1 Many substances will dissolve in it. Water has a dipole, so ionic substances which are made of positive and negative ions will dissolve in it. For example salts like sodium chloride will dissolve as the positive and negative ions separate and become surrounded by water molecules. Polar substances (compounds with covalent bonds, but with small charges) will not dissolve in most solvents, like ethanol, except for water. Water can also carry many non-polar molecules. They would form colloids where the solute particles are larger than the solvent particles Some substances don't dissolve in water and instead form emulsions (oil and water) or suspensions where liquid and solid mix when constantly stirred.
2.1.2 As chemical reactions in cells occur in water the ability to act as a solvent is vitally important
2.2 Water has one of the highest known surface tensions
2.2.1 Surface tension is high in water due to the hydrogen bonds 'pulling' down on the molecules. Because there is no attraction between water and air a thin layer of surface tension is created. This is vital to plants and life in water masses.
2.3 The water molecule is amphoteric
2.3.1 This means that it can act as either an acid or a base. (H+ Ions as a proton donor, OH- ions as a proton accepter) This means that water is an ideal medium for biochemical reactions within cells. Also acting as a buffer to prevent reactions from changing PH.
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