Water,H2O, is one of the most important chemical compounds on earth, and is commonly referred to as the basis of life on earth, because it is used in all type of chemical and biological processes, e.g. solvent, protein folding, stability of nucleic acids etc. Water is found in 3 states (solid, liquid, and gas), and is the most abundant naturally occurring substance on earth, covering 75% of the earth surface.
Water consists of 2 hydrogen atoms and 1 oxygen atoms, (held together by covalent bonds between the O-H atoms) and 2 lone pair of electrons on the oxygen atom, resulting in the formation of a bent shape with a bond angle of 104.5⁰. These 2 lone pair of electrons means that water has a tetrahedral structure where oxygen is bonded to 4 hydrogen atoms; 2 covalent bonds and 2 hydrogen bonds (General Chemistry, 2011).
Hydrogen bonding ‘is a specific type of dipole-dipole interaction between the hydrogen atom in a polar bonds, and an electronegative O, N or F atom’ (Quotes from General Chemistry, 2011 page 405), and is the strongest type of intermolecular force. Hydrogen bonds in water (Figure 1) mean that water has a high specific heat capacity, this is because, as hydrogen bonds are strong a large amount of heat (increases the kinetic energy of water molecules), is needed to break them, however water can absorb a large amount of heat and its temperature only increases slightly, and is the reverse when heat is released i.e. its temperature only decreases slightly (General Chemistry, 2011). The presence of hydrogen bonds between water molecules, allowing them to stick together mean shows that water is highly cohesive (Biochemistry, 2011). A special type of cohesion is surface tension, in which tension is caused by water molecules outside the system, which align by forming hydrogen bonds with other water molecules, this forms an ordered arrangement.
The oxygen atom in water molecules contain 2 lone pair of electrons which have a negative charge and therefore repel each other, thus they move further apart. This consequence of this movement of lone pair is the O-H bonds move closer together and due to water’s bent shape ‘the distortion of charge is asymmetric’ (Quotes from Biochemistry, 2011 page 8). However, this means the hydrogen atoms now have a slightly positive charge (δ+), meaning that water is a polar molecule (Figure 2). This property is highly important in allowing water to carry out its many functions.(Biochemistry, 2011)
Non-polar molecules cannot form hydrogen or ionic bonds. When in solution water surrounds non-polar molecules which become well ordered and therefore have lower entropy, unlike free water molecules in solution. However, when two non-polar molecules surrounded by water molecules come together, the water ‘cages’ (Quotes from Biochemistry, 2011 page 9) join together and some water molecules are released, increasing the entropy of the system (Biochemistry, 2011). The ability for...