This is a A* written piece using the AQA Biology Textbook about water and its importance to life.
This could come up as an essay in AQA Paper 3 Biology.
Between water molecules there are hydrogen bonds 2 hydrogen atoms are
bonded to one oxygen atom via covalent bonds. There are positive and
negatively charged regions of adjacent water molecules. As hydrogen bonds
are weak, they can constantly break when there are few of them. When
hydrogen bonds form it is called a cohesion. When there are a lot of hydrogen
bonds however, a strong structure is formed.
As water is a solvent, some substances can dissolve in it. Waters polarity makes
it a useful solvent as the ions get surrounded by water molecules, so they
dissolve. We can dissolve many minerals in water which is why the water we
tend to use is rarely pure. The solvency of water allows multiple biochemical
reactions to take place in the cell cytoplasm. Waters solvency also allows
substances to be transported around organisms.
Water has a very high specific heat capacity. This is because energy is needed
to break the bonds. So, water resists temperature changes, thus allowing a
more stable environment for aquatic organisms. Water also has a very high
latent heat of vaporisation; this is the amount of heat that is needed to turn a
substance into a gas. So, sweating, the evaporation of water, can provide a
significant cooling effect. Latent heat of fusion is the amount of heat needed to
be lost to freeze a substance. This again allows a stable environment.
Water is less dense as a solid than a liquid. A lattice is formed when water
freezes and each molecule forms hydrogen bonds with four others. So,
because of this ice floats on water which allows aquatic organisms to survive in
water under ice.
Water molecules are very cohesive which helps water transport in plants as
they stick together. They are also very adhesive, so they tend to stick to other
molecules that are charged. Water molecules adhere to walls of xylem vessels
as it is drawn up the stem from the roots. Water can be lifted by forces applied
to the top and so can be drawn up xylem vessels of tree trunks by forces in
their leaves.
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