Question

The Water Molecule

a. Sketch in detail how the molecular structure of H2O determines the unique properties of water in terms of Latent Heat, Heat Capacity, Solvent Power, and Surface Tension. b. Give three detailed examples of ways that these properties of the water molecule determine the chemical and physical behavior of the ocean (think in terms of Salinity, Temperature Profiles, Water Density, Ocean Layering, Ocean pH, Oceanic vs Continental Climate, etc.)

Answer 1

Water molecule is formed by 2 atoms of Hydrogen and one atom of oxygen. As shown below

Due this atom geometry, there's a partial negative charge surrounding Oxigen atom and a partial positive charge on the vicinity of Hydrogen atoms. This charge distribution al arround the molecule lets to form 'Hydrogen bonds' between molecules.

One Hydrogen from one molecule interacts with the Oxygen from a different molecule, forming a Hydrogen Bond. This happens on all the molecules of water, creating something like a network of molecules strongly bonded.

Due the strenght of the HYdrogen Bonds, the molecules of water even in liquid state, are very strongly bonded, this means that you will need to put a lot of energy into the liquid for heating it, and once the liquid water is heated, the heat will remain for a long time. So the Latent Heat and Heat Capacity values of water are due the molecular structure of the molecule and the capacity of the molecules of forming 'Hydrogen bonds' between molecules.

On the other hand, the network of walter molecules on the surface (created by the Hydrogen Bonds) makes a hard surface, this situation is known as Surface Tension

The charge distribution on the molecule allows the water to become on the best solvent. Negative charges of the molecule interacts with the positve charges of a solute and the oposite will hapen with the positve part of the molecule. For this reason, water acts as a good solvent, due his capacity to solvate (surround) positive and negative charges.

Due the high Latent Heat and Heat Capacity of the water, the ocean may act as a system that buffers climate changes. Larges amounts of heat can be stored on large amount of water (latent heat) and then this heat is transferred to the atmosphere for heating it. On the other hand occurs the opposite, large amounts of heat are transferred from the atmosphere to the ocean and this colds the amtmosphere.

The high salt concentration on the ocean is due the capacity of the water of dilute salts thanks to the charge distribution on the molecule. Salts are formed by an anion and a cation ions, water's Hydrogens solvates anions while water Oxygen's interacts with cations