 SWBAT summarize what causes surface tension in water.  SWBAT define solution, solute, solvent and polar molecule.  SWBAT summarize the steps of dissolving a substance.  SWBAT percent composition problems.  SWBAT describe solubility and be able to interpret a solubility curve.  SWBAT describe why water is the universal solvent.

 Surface Tension: of a liquid results from an imbalance of intermolecular attractive forces, the cohesive forces between molecules: › A molecule in the bulk liquid experiences cohesive forces with other liquid molecules in all directions. › A molecule at the surface of a liquid experiences only net inward cohesive forces.

 Surface Tension: › vX0jmhJ4 vX0jmhJ4 › vdNbftOY vdNbftOY

 Solutions: a mixture of two or more substances that is uniform at the molecular level.  Solutions exist in every phase: solids, liquids, and gases.

 Solid: A solution of two or more solids is an alloy. o Steel (a solution of Iron and Carbon)  Liquid: Liquid solutions may contain solids, liquids, and/or gases. o Salt Water o Soda  Gas: A solution of two or more gases. o Air (a solution of nitrogen, oxygen, argon, carbon dioxide and traces of other gases

 Solvent: the component of a solution that is present in the greatest amount.  Examples: o the water in soda is the solvent. o The water in salt water is the solvent. Water dissolves sodium chloride (salt) to form a solution of sodium ions (Na + ) and chlorine ions (Cl - )

 Solute: any component of a solution other than the solvent.  Salt is the solute in a salt water solution.  What is one of the solutes in a soda?

 When solute particles are evenly distributed throughout the solvent, the solute is dissolved  Dissolve: to separate and disperse a solid into individual molecules or ions in the presence of a solvent

Ionic compounds are solid “salts” with a crystalline structure 1. Polar solvent (H 2 O in this case) surrounds the solid crystal

2. NEGATIVE charges concentrated on the O of H 2 O bond to positive ion of the ionic compound 3. POSITIVE charges concentrated on the H’s of H 2 O bond to negative ion of the ionic compound

4. H 2 O “tugs” apart the salt crystal ion by ion o Cation (Na+): pulled by negative oxygen end o Anion (Cl-): pulled by positive hydrogen end

5. Eventually all ions are surrounded by water molecules and are said to be in an AQUEOUS SOLUTION (THEY ARE DISSOLVED) the solid is “gone”

 Solubility: the amount of solute that can be dissolved in a specific volume of solvent under certain conditions.  Solubility is always given at a specific temperature since temperature strongly affects solubility.

 Insoluble: a substance is insoluble in a particular solvent if it does not dissolve in that solvent. o Oil is insoluble in water  Saturated: a solution is saturated if it contains as much solute as the solvent can dissolve.

 Concentration: the ratio of solute to solvent in a solution.  Concentration = ___mass of solute___ X 100% total mass of solution  Example: o A 10% sugar solution contains 10g of sugar for every 90g of water

 When a solute like sugar is mixed with a solvent like water, two processes are actually going on continuously. › Molecules of solute dissolve and go into solution. › Molecules of solute come out of solution and become “un-dissolved.”  Equilibrium occurs when the rate of dissolving equals the rate of coming out of solution. The solution has a maximum concentration of dissolved solute.

 Supersaturated solution: there is more dissolved solute than the maximum solubility.

 Solubility of gases in liquids increases with pressure. 2 was dissolved in liquid at a high pressure.  Soda is fizzy because the CO 2 was dissolved in liquid at a high pressure.  When you pop the tab on the soda can the pressure is released, causing immediate supersaturation of the solution.  Dissolved oxygen is essential to underwater life

 Overall charge is neutral  Charges are unequally distributed on each side of the molecule  H 2 O is a polar molecule

 Water is a good solvent because of the way the H 2 O molecule is shaped.  A water molecule has a negative end (pole) and a positive end.  A molecule (like water) with a charge separation is called a polar molecule.

 In general, like dissolves like: › water dissolves polar substances › non-polar solvents dissolve non- polar substances