Water

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Biological Compounds ­ Water High Surface Tension:
Solvent: The molecules at the surface form stronger
Atom: smallest particle. Water is a solvent, which means that it is a bonds. Water has the largest surface tension
Molecule: a group of bonded atoms joined by liquid into which substances can dissolve of all liquids except mercury at ordinary
atomic or covalent bonding. into. temperatures. This provides a habitat for
Elements: a group of the same molecules. aquatic organisms.
Compounds: atoms of different chemical Hydrophilic: water loving. In a pond the surface tension is strong
structure joined together. Hydrophobic: water hating. enough to support light objects such as
paper-clips and pond skaters.
Water: Water is a good solvent because charged or
The human body is made up of 80-90% of polar molecules such as salts, sugars and High Latent Heat:
water, which helps the body to maintain body amino acids dissolve readily with water. Water has a high latent heat, which means
temperature by barring the heat energy. Therefore, they are called hydrophilic that a lot of heat energy is needed for it to
Plants require water to transport nutrients substances. change from a liquid into a vapour state.
that are dissolved within the water. Water Therefore, the body uses salt water, sweat,
can also be found in the plasma of blood Uncharged or non-polar molecules such as to cool the body down as the excess heat is
cells. lipids do not dissolve readily in water and are used in the evaporation of the sweat.
known as hydrophobic.
Water molecules join by covalent bonding, Density Fluctuations:
and form a hydrogen bond. This allows chemical reactions to take place Water has a maximum density at 4°C. water
Water is a polar molecule and has no over all in solution, and the transport of materials. in its solid form of ice is less dense than
charge. The oxygen atoms have a slight water and so floats upon the surface.
negative charge while the hydrogen atom High Specific Heat: The ice forms an insulating layer and allows
has a slight positive charge. A large amount of heat energy is needed to organisms to survive underneath.
raise the temperature of water by just 1°C.
When two water molecules join together, the This is because the hydrogen bonds restrict Transparent:
opposing charges on the hydrogen and the movement of the water molecules. This provides a habitat for aquatic
oxygen atoms attract each other to form This enables enzymes to work effectively organisms, and allows the light to pass
hydrogen bonds. Individual hydrogen bonds and provides a stable habitat for aquatic through, enabling aquatic plants to
are very weak, but they can form a strong organisms. photosynthesise effectively.
lattice when there are a lot of them. This is
called cohesion. The high specific heat prevents large
fluctuations in the water temperature, and is
Properties of Water: important in keeping the temperature of
Water has six main properties that make it aquatic organisms stable so that they don't
important to life on Earth;- have to endure the extremes of temperature.
- water is a solvent,
- water has a high surface tension, Cohesion:
- water has a high specific heat The strong lattice provided by the hydrogen
capacity, bonds allows columns of water to be drawn
- water has a high latent heat, up xylem vessels in tall trees.
- water's highest density is at 4°C,
- water is transparent.

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