AS WJEC Importance and properties of water

An essay on the importance and the properties of water.

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The Importance of water
Wherever one looks in the biological world, water is vital for all life. It is simple to state that
without water (or H2O) there would be no life on the planet. Even humans themselves are
made up of around 60% water. This is due to the huge variety of
different properties that water has, giving it so many uses. In this
essay, these different properties are going to be explored and
explained.
One of the most important properties of water is that it is a polar
molecule. Water contains two hydrogen atoms and one oxygen
atom, they then combine, sharing electrons in a covalent bond as
shown in figure 1. However, the sharing is not equal, the oxygen
attracts the electrons more strongly than the hydrogen, resulting in
the oxygen having a more negative charge and the two hydrogen
atoms having positive charges. This is important because the slight
polarity of the water molecule attracts it to the other molecules
around it, as shown in figure 2, creating a weak hydrogen bond.
These hydrogen bonds serve many vital purposes. Firstly, it results
in water being highly cohesive. This is why when water is dropped on an impermeable
surface, it forms in small droplets, whilst if a liquid based on a non-polar molecule such as
olive oil, it would spread out and not stay stationary. It is this cohesive feature that allows
tall trees to get water up to the sight of photosynthesis in their leaves from their roots. As
the water transpires from the stomata of the
leaf, more water is "pulled" up behind it like a
chain through the capillaries in the xylem in the
tree allowing trees to continue photosynthesising.
The second result of the water cohesion is that
water has a very high surface tension. This is
important for life forms such as pond skaters
to move across the surface of the water
without falling into it, as shown in figure 3.
They are able to do this because the force of
their bodyweight is not great enough to break the surface tension, more
specifically the hydrogen bonds between the water molecules and so they
do not fall in, humans however have place to much of a force on it and that is why we fall in.
The hydrogen bonds make it very hard for the water to make a change from being a liquid to
gas, this is why it has a high boiling point of 100OC and more precisely, a very high specific
heat capacity because the networks of hydrogen bonds link all the water molecules together
and so large amounts of energy are required to break the bonds. This has two major
purposes. Firstly, it is used in humans for cooling down in the form of sweat as huge
amounts of heat are removed from the body, used to turn the water from a liquid into a gas
and so the heat leaves the body cooling it down. On the other hand, it also holds its heat.
Oliver Cobbold

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The Importance of water
This allows the correct heat for optimum enzyme activity inside cells to be held. This is due
to the high water content in the cells.
With most molecules, when they turn from a liquid into a solid, they become
denser as they become more rigid. This however is not the case with H2O,
once again due to the hydrogen bonds. When water freezes, the hydrogen
bonds force the water molecules into a much more regular lattice shape.…read more

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The Importance of water
This is important because as the turgid cells push against each other, this holds the plant
upright, acting much like a skeleton for the plant. When the opposite of this happens, and
there is not enough water in the vacuole, the cell becomes flaccid and cannot keep the plant
upright. The result of this being the plant wilting and so no longer being able to
photosynthesise and make sugar for respiration, therefor the plant dies.…read more

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