Water high heat of vaporisation mean the boiling

Water
chemistry is in fact the most studied by scientists but the least understood
due to its many unusual properties and unique behaviours that are very
different compare to other substances. For example, ice is one of the very few
known existing substances that floats on its liquid state, this is because most
substances become denser than their liquid state when they condense, and thus,
sink to the bottom; whereas water has the highest density of 1g/cm3
i
at 4°C ii,
any temperature below 4°C is leading to crystallisation into a rigid
lattice structure held together by hydrogen bond, increasing the space between
moleculesiii
and therefore forming ice that is less dense than the liquid water. High
specific heat and high heat of vaporisation mean the boiling point and freezing
point are abnormally high for water (100°C and 0°C respectively) compare to molecules
with similar sizes; this is because of the formation of hydrogen bonds that
requires a large amount of energy when water condenses from gaseous state and
also freezes from liquid state into solid state; creating resistance on extreme
temperature changes, make sure there is a minimal effect on species living in
water. As a solvent, it can carry nutrients in runoff, in groundwater,
and inside organisms. Its adhesive, cohesive, and elastic properties allow it
to form into droplets and make waves.

 

The importance of water in our daily lives and its
complexity are the reasons why
water models are very useful in terms of predicting the behaviour and
properties of water molecules under varies conditions for different research purposes.

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There are generally two types of modelling water – numerical computer models
and physical modelsiv.

Physical models use real water and normally with scaled structure to model
processes involve behaviours of water such as highly turbulent 3D flow
patterns, debris behavior, wave action, and sediment transport that scientists do not yet
understand well enough to model numerically. Although physical models give very
accurate modelling, it is usually expensive and each model would take times to
develop.

 

Increase in
computer stimulation power in recent decades has improved the ability to
perform difficult calculations. The research stated that there are over 46
distinct computational modelsv
to predict the physical properties of liquid. Each model is developed
specifically targeting one physical structure or parameter, having 46 models
shows the lack of reproducing abilities of each individual model and none of
the model gives an accurate representation of real water, therefore, once again
supports the statement of the complexity in water structure and water
behaviour. All the models differ from three aspects in generalvi:
The bond geometry, i.e. the OH bond length and H-O-H bond angle of the model;
the charge distribution, i.e. location of the negative charge(s); and the
target properties, i.e. the properties of real water that the model is
developed to fit the potential parameters.

iDensity
of Water, https://www.simetric.co.uk/si_water.htm, (accessed December 2017)

 

ii F.

Franks, Introduction – water, the unique chemical, in Water A
comprehensive treatise, Vol. 1, Ed. F. Franks (Plenum Press, New York,
1972) pp. 1-20.

 

iii A.

Marie, “Why Is Water More Dense Than Ice?”, https://www.thoughtco.com/why-is-water-more-dense-than-ice-609433,
(accessed January 2018)

 

iv How
water is modeled, http://learn.genetics.utah.edu/content/earth/howmodeled/,
(accessed December 2017)

 

v B.Guillot,
A reappraisal of what we have learnt during three decades of computer
simulations on water, Journal of Molecular Liquids, 2002,
Volume 101, 219-260.

 

vi
C. Vega, J. L. F. Abascal, M. M. Conde and J. L. Aragones, What ice can teach
us about water interactions: a critical comparison of the performance of
different water models, Faraday Discussiosn, 2009, volume 141,
251-276.