Water- Essential for Life

The Blue Planet Oceans cover nearly 71% of Earth’s surface, most obvious feature of Earth as seen from space. http://swofford8.wikispaces.com/Hydrosphere

Fresh water- page 268 Fresh Water Type Location Amount Frozen Water Poles, Glaciers, Winter Ground Water Found in aquifers, underground rivers, in porous rock Surface water Ponds, Lakes, rivers Vapour Atmosphere

States of Water- Density

Hydrogen bonding (electric attraction) Ice Liquid

Water- Surface Tension

Water: the universal solvent Solutions in which water is the solvent are called aqueous solutions Polar molecule Oxygen atom has a partial negative charge Hydrogen atoms have a partial positive charge

Dissolution of Solid Solute What are the driving forces which cause solutes to dissolve to form solutions? 1. Covalent solutes dissolve by attraction between polar ends and solvent’s poles 2. Ionic solutes dissolve by dissociation into their ions.

Solution Animation

Solution Process - Ionic Compounds Attractive forces between anions & cations in solid versus Attractive forces between water molecules and cations & water and anions

The Solution Process Molecular Compounds Covalent molecules that are small and have “polar” groups tend to be soluble in water 4

Likes dissolve likes Molecules that are similar in structure tend to form solutions Which of these molecules will dissolve in water?

Ionic Solutions How do we know ions are present in aqueous solutions? The solutions _________________________ They are called ELECTROLYTES HCl, MgCl2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions.

Molecular Solutions Some compounds dissolve in water but do not conduct electricity. They are called nonelectrolytes. Examples include: sugar ethanol ethylene glycol

Electrolytes in the Body Carry messages to and from the brain as electrical signals Maintain cellular function with the correct concentrations electrolytes

Definitions Solutions can be classified as saturated or unsaturated. A saturated solution contains the maximum quantity of solute that dissolves at that temperature. An unsaturated solution contains less than the maximum amount of solute that can dissolve at a particular temperature

Supersaturated Solutions Under some conditions, more solute will dissolve than “saturated”. Heat most salts in water, the solubility increases. Slowly cool down the solution. Extra solid doesn’t come out easily. Something happens to cause crystals to form. Then, zap, they form. Examples: fudge, honey

Supersaturated Sodium Acetate One application of a supersaturated solution is the sodium acetate “heat pack.”

Homework Page 274 1,2, 4a), 5, 6