Water

Unique Structure of Water

Dipole Moment Dipole moment: Used to depict the strength of the charge and the distance between the charge in a polar molecule. A dipole moment allows a molecule to reach neutrality. Created when a molecule has slight “-” & “+” regions.

Structure of the Water Molecule Covalent Bonds & Hydrogen Bonds in H2O Hydrogen Bond Covalent Bond

Unique Properties of Water Adhesion Cohesion Capillary action High surface tension High Specific Heat/heat capacity High heat of vaporization Less dense as a solid than a liquid

Properties of Water Cohesion, Adhesion cohesion = water’s ability to attract to other water molecules through its polarity adhesion = water’s ability to attract to different materials other

Properties of Water Capillary Action Capillary action is created by the adhesive and cohesive properties of water. Capillary Action - The ability of water to rise through a narrow tube due to water’s adhesive and cohesive properties. Ex: Water movement up a straw Ex: Water movement in a tree

Properties of Water High Heat Capacity In order to raise the temperature of water, the average molecular speed has to increase. It takes much more energy to raise the temperature of water compared to other solvents because hydrogen bonds hold the water molecules together! Water has a high heat capacity. “The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius.” High Heat Capacity

Heat of Vaporization The amount of heat needed to turn a liquid into a gas Water has a very high heat of vaporization

Water is the solvent of Life! Properties of Water Universal Solvent Water is the solvent of Life! Solute – substance dissolved in a solvent to form a solution Solvent – fluid that dissolves solutes Example: Ice Tea – water is the solvent and tea and sugar are the solutes

Properties of Water Density Ice (solid form of water) is less dense than the liquid form of water! Each molecule of water in an ice cube is bound to four of its neighbors by 4 hydrogen bonds.

Properties of Water Covalent bonding Polar covalent bond – a type of covalent bonding where there is unequal sharing of electrons between atoms Non Polar Covalent bond – A type of covalent bond where electrons are shared equally

Acids and Bases

Acids and Bases Acid – any substance that creates free hydrogen ions (H+) ormprotons when in solution. Ranges from pH 0 < 7 Base – any substance that creates free hydroxide (OH-) ions when in solution. Ranges from pH 7 > 14 pH Scale – Ranges from 0 – 14 Logarithmic Scale (gets 10x bigger/smaller) Distilled water is pH 7.0 or neutral. Why? H2O H+ + OH-

Acids and Bases Buffer – an aqueous solution that resists changes in pH. The pH of a buffer remains constant. H2CO3 H+ + HCO3- Carbonic acid bicarbonate ion

Hydrologic Cycle