Properties of H20 Why water is special

Polarity Polarity describes the distribution of electrons in a molecule Polar molecules have an uneven distribution of electrons. Example: Water + -

Cohesion Cohesion is the attractiveness of molecules of the same substance to one another. Water has a high cohesion, which explains why water beads on surfaces. The water molecules are so attracted to themselves that they do not spread apart readily. This attraction is due to hydrogen bonds between H+ of one atom & O- of another. Also called surface tension YouTube: Surface Tension YouTube: Jesus Lizard Hydrogen Bonding

Adhesion Adhesion is the attractiveness of molecules between different substances Water also has high adhesiveness. Explains why water attempts to creep up the sides of a graduated cylinder and form a meniscus.

Solutions and Mixtures A mixture is a substance that is made of two or more elements physically mixed together Example: Mixing Skittles and M&Ms together A solution is a type of mixture where one substance is dissolved in another. Solute- the substance that is dissolved Solvent- the substance that does the dissolving

Water as a solvent Water is often referred to as the “Universal Solvent” because of it’s ability to dissolve such a wide variety of substances. GO WATER!!!

The pH Scale (Acidic, Basic, Neutral) pH is a measure of the concentration of of H+ ions (pH=power of Hydrogen) Describes how acidic or basic (alkaline) something is pH 0-6 = acid – substance forms H+ ions in water Ex: Lemon juice (pH=2) pH 7 = neutral Ex. Pure water and blood pH 8-14 = base (alkaline) – substance forms OH+ ions in water Ex. Ammonia (pH= 12)

Buffers Buffers: Solutions that prevent sudden changes in pH. Neutralization reaction: HCl + NaOH → HOH + NaCl (HOH is the same as H2O) Another way to say it: HCl + NaOH → water + salt Buffers help living organisms maintain internal stability. This is called ______________________.