Water Emergent Properties of Water – Water is perhaps the most important Molecule found on the surface of the Earth. It makes up roughly 75% of Earth's surface and between % of the volume of our cells. It is no wonder that the evolutionary tree starts with organisms that resided in it.

Water’s Unique Properties - Polarity – Very polar, bent, & able to form weak chemical bonds (H or dipole) with many other molecules (universal solvent) Cohesion - the ability of water to form and break bonds with itself. (aids in the transport of water in plants) Adhesion - the ability of water to stick to other substances (the walls of a graduated cylinder) High surface tension - inward force that adds to the viscosity of water (allows it to form a droplet)

Water’s Unique Properties – Universal Solvent Water dissembles ionic substances by forming hydration shells (sphere of water around an ion). Water is the solvent, the ionic substance is the solute, and the liquid is named an aqueous solution. – Breaks bonds of macromolecules via the process of hydrolysis – Forms bonds in macromolecules via the process of dehydration synthesis Attraction to water – Things that are attracted to water (polar molecules) without dissolving are said to be hydrophilic – Things that repel water (non-polar molecules) are said to be hydrophobic.

Water’s Unique Properties – Self Ionization Water constantly dissociates to form the ions H + and OH -. As a result the free proton binds with a free water molecule forming the hydronium ion(H 3 O + ) – The pH of the liquid if it is pure water is 7 and the concentration of both the hydroxide and hydronium ions equal

pH Scale Acids and Bases – Acids…Any substance that donates a proton (H +) in solution is an acid. Acidic solutions have a pH < 7.0 – 0 is strongest acid – Turns blue litmus red – Bases…Any substance that accepts a proton (H +) in solution is an base. Basic solutions have a pH > 7.0 – 14 is strongest base – Turn red litmus blue – Buffer… a weak acid or base that absorbs and releases H + ions to keep pH from changing drastically Bicarbonate buffer system HCO H +  H 2 CO 3  H 2 O + CO 2