Properties of Water

Many of the properties of water link back to its structure and bonding. 
The oxygen atom is covalently bonded to two hydrogen atoms, and has two non-bonding electron pairs. The oxygen has a higher electronegativity than the hydrogen, so these bonds are polar. This means that the oxygen has a partial negative charge, as the electrons are more strongly attracted to it, and the two hydrogen atoms will have a partial positive charge, as the electrons are drawn away from them. Water molecules are able to form hydrogen intermolecular bonds. 

Group 16 Hydrides:
Water is one of the Group 16 Hydrides (as oxygen is a group 16 element, and it is bonded to hydrogen, H2O)
However, water defies many trends found in this group. Generally, the melt/boil point of these compounds increase going down the group, due to increased dispersion forces. Despite being the smallest hydride, it has high melting and boiling points.

 Properties of Water include:
Relatively high melting/boiling temperature
High latent heat values
High specific heat capacity
Thermally stable
Expands on freezing
Conductor of heat
High surface tension
Solvent

 High Melting and Boiling Point:
Water has a high melting and boiling point, this is due to water being able to form 4 hydrogen bonds at a time (one from each hydrogen, and two from the oxygen) and therefore, a large amount of energy is required to disrupt all these bonds. 

 High Latent Heat Value:
Latent heat is the amount of energy absorbed or released by a substance as it undergoes a change of state, and is represented by l and kJ mol-1 and j kg-1. From solid to liquid: LH of Fusion, from liquid to gaseous: LH of vaporisation. It is the amount of energy required to break the intermolecular bonds, without change in temperature. As water has strong hydrogen bonds, it has a high latent heat value, with 6.02 kJ of energy required to change one mole of solid to liquid. 

 High Specific Heat Capacity
The amount of energy needed to raise the temperature of one gram of the substance by one degree Celsius. Water has a high heat capacity as it takes a lot of heat/energy to break the hydrogen bonds. This also leads water to be thermally stable, and thus better for organisms to live in. The equation is given at right.

 Density
Density is a measure of the amount of mass that is contained in a certain volume of that substance. It is calculated by d=mass divided by volume. The official symbol is actually p but d is often used. The density of water depends on its temperature and state. Water expands on freezing as the molecules arrange into a regular lattice that is less dense than at liquid.

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