The CHEMISTRY of WATER Water is a Chemical H20

Water plays an important role as a chemical substance. Its many important functions include: being a good solvent serving as an excellent coolant both mechanically and biologically acting as a reactant in many chemical reactions.

Structure Means Function

The bonds which hold the hydrogen and oxygen together are called covalent bonds - they are very strong. The water molecule maintains a bent shape (bent at degrees actually) because of – the tetrahedral arrangement around the oxygen – the presence of lone pair electrons on the oxygen.

What are Lone Pair Electrons? The electrons not involved in the covalent bonds The pairs of electrons that are left alone. (represented by the double dots) They are very negative - containing two negative electrons each - and want to stay away from each other as much as possible. These repulsive forces act to push the hydrogens closer together

What's your Point? The shape and structure of a molecule is an important determinant of its function. The importance of the bent structure of water is that it provides water with two distinct "sides": – One side of the water molecule has two negative lone pairs, – while the other side presents the two hydrogens (positive).

Water is also highly polar The lone pairs are negative The hydrogens are slightly positive.

Hydrogen Bonding Because water has a slightly negative end and a slightly positive end, it can interact with itself and form a highly organized 'inter- molecular' network. The positive hydrogen end of one molecule can interact favorably with the negative lone pair of another water molecule.

Hydrogen Bonds are weak, but they are important!! There is strength in numbers! The polarity allows water to interact with an electric field The polarity allows water to interact with other polar molecules - which is how substances become dissolved in water.

Water is Weird !? Ice Floats - That's very weird. The solid state of most things are much denser than the liquid state and therefore sink. To understand why look at the molecular arrangement of solid water (ice) and liquid water.

Specific Heat Another result of the Hydrogen bonding network is that water has a very high Specific Heat. Baked potato effect. Once heated, water takes a very long time to cool off. Or in reverse, it takes a lot of heat to make water hot.