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46257
WATER
Descrição
Biology (Topic 1: Lifestyle, Health and Risk) Mapa Mental sobre WATER, criado por Jackj888 em 14-04-2013.
Sem etiquetas
biology
topic 1: lifestyle
health and risk
biology
topic 1: lifestyle, health and risk
Mapa Mental por
Jackj888
, atualizado more than 1 year ago
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Criado por
Jackj888
mais de 11 anos atrás
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Resumo de Recurso
WATER
CHEMISTRY OF WATER
Each water molecule is slightly polarised,
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-
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.
IMPORTANCE OF WATER
Water is an unusual and excellent solvent
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.
As chemical reactions in cells occur in water the ability to act as a solvent is vitally important
Water has one of the highest known surface tensions
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.
The water molecule is amphoteric
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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