DO NOW What is a solution AGENDA w

DO NOW What is a solution? AGENDA w Introduction to solutions w Solutions vocabulary REMINDERS w

What do the following pictures have in common? Air Salt water Bronze (copper + tin) They are all “solutions…” A solution is a homogeneous mixture in a single phase…

Review w Element—substance that cannot be broken down into simpler substances (periodic table) w Compound—a substance made of atoms of more than one element bound together (H 2 O, CO 2, Na. Cl) w Mixture—a combination of more than one pure substance (Salt water, Powerade, Salad)

Mixture Review w Mixture—a physical blend of two or more substances w Heterogeneous mixture—one that is not uniform in composition w Homogeneous mixture—one that has a completely uniform composition

Homogenous Mixture w Homogeneous mixture—one that has a completely uniform composition n Alloy – uniform mixture of two metals l Amalgam (silver + mercury), steel (iron + carbon)

Mixture Review

Mixture REVIEW w You can separate mixtures by PHYSICAL means n n n Distillation Separation Chromatography

Polarity w Polar moleculesn n one end of a molecule is slightly positive and the other end is slightly negative Unequal sharing of electrons w Nonpolar moleculesn n charges are equal and cancel out each other Equal sharing of electrons

Water w Water is a polar molecule!

p. 398 summary Solutions Colloid Type Particle size Settle Tyndall upon effect standing (Scatter light) Homogeneous 0. 01 -1 nm No (cannot no Heterogeneous 1 -1000 nm No (cannot Yes Suspension Heterogeneous be filtered) Greater than 1000 nm Yes (can be sometimes filtered)

Solution Chemistry w Solution—a homogeneous mixture n n 1. Solute—dissolved particles in a solution 2. Solvent—the dissolving medium in a solution (usually water, the universal solvent)

Kool-Aid Solution w Kool-Aid Juice is the SOLUTION w Kool-Aid powder and Sugar are the SOLUTES w Water is the SOLVENT

Solutions are homogeneous mixtures that could be solid, liquid, or gaseous solute solvent Gas Gas Liquid CO 2 in water Liquid Gas Oxygen in nitrogen Water in air Liquid Alcohol in water Liquid Solid Mercury in silver and tin (dental amalgam) Liquid Sugar in water Solid Copper in nickel (alloys)

Soluble vs. Insoluble w Soluble—dissolves completely so that solution looks transparent (free of any floating particles w Insoluble—does not dissolve completely; solution is cloudy

How does dissolving takes place? w What happens when salt is dissolved in water? Na. Cl Na+ + Cl-

Complete the dissociation of the following salts: w KCl w Mg. Cl 2 w Al. Cl 3 w Mg. F 2 *

Complete the dissociation of the following acids: w HCl w HBr w HC 2 H 3 O 2 w HNO 3 *

Solution Chemistry w Electrolytes—compounds that conduct an electric current n ALL ionic compounds; Na. Cl, Cu. SO 4, Na. OH w Nonelectrolytes—Compounds that do not conduct an electric current in either aqueous solution or the molten state n Many molecular (covalent) compounds; carbon, sugar, alcohol

Electrolytes vs. Nonelectrolytes

Electrolytes vs. Nonelectrolytes w Weak Electrolyte—only a fraction of the solute exists as ions; partially dissociate w Strong Electrolyte—almost all the solute exists as separate ions; completely dissociate

Strong electrolyte in solution. Weak Electrolyte in solution.

Electrolytes vs. Nonelectrolytes w STRONG ELECTROLYTES n Strong acids (HCl, H 2 SO 4, HNO 3, HBr, HI, HCl. O 4) n Strong bases (Na. OH, KOH, etc. ) w WEAK ELECTROLYTES n Weak acids (Vinegar, acetic acid, CH 3 COOH) n Weak bases (Ammonia, NH 3) w NONELECTROLYTES n Molecular compounds n Nonmetal bonded to nonmetal

Electrolytes vs. Nonelectrolytes w More moles of ions in solutions, the more conductivity w Which salt would give more ions: Na. Cl or Mg. Cl 2? w So, which will conduct electricity more/be a better electrolyte? w Look back at the dissociation reactions and determine the better electrolyte.

Solubility w Solubility—the amount that dissolves in a given quantity of a solvent at a given temperature to produce a saturated solution. n Solubility is often expressed in grams of solute per 100 g of solvent

Water and Solubility? w REMEMBER water is a POLAR molecule n Polar means electrons are not spread evenly throughout the molecule w Polar molecules dissolve polar molecules n Water can dissolve ammonia w Nonpolar molecules dissolve nonpolar molecules n Octane (gasoline) can dissolve CO 2 w LIKE DISSOLVES LIKE!!!!

Solution Concentration w Concentration—the quantity of solute dissolved in a given quantity of solution n Three ways to describe a solution Unsaturated solution l Supersaturated solution l

Solubility w Unsaturated—a solution that contains less solute than solvent w Saturated—a solution that contains the maximum amount of solute for a given amount of solvent at a constant temperature w Supersaturated—a solution that contains more solute than it can theoretically hold at a given temperature; crystals form

Solubility w Two liquids are said to be MISCIBLE if they dissolve in each other n Water and ethanol dissolve in each other w Liquids that are insoluble in each other are IMMISCIBLE. n Oil and water do not dissolve in each other

MISCIBLE Water and alcohol IMMISCIBLE Water and oil

Gas Solubility w Henry’s Law—as the pressure of the gas above the liquid increases, solubility of the gas increases and vice versa

Gas Solubility w Henry’s Law S 1 P 1 = S 2 P 2 w S = solubility w P = Pressure

Gas Solubility and temperature w As temperature increases, the solubility of a gas tends to decreases.

Factors Affecting Rate of Dissolving of solid solutes w SURFACE AREA n Solutes with larger surface area dissolves faster l Smaller pieces = larger surface area w Smaller pieces dissolve faster than larger pieces

Factors Affecting Rate of Dissolving of solid solutes w STIRRING n Stirring or shaking a solution helps the solute dissolve faster l Stirring or shaking moves dissolved sugar away from undissolved sugar crystals

Factors Affecting Rate of Dissolving of solid solutes w TEMPERATURE n Solid solutes dissolve faster when the solvent is hot (except gases !) l When substance is heated, particles move faster causing more collisions between particles

Solubility Curves w Solubility curves (graphs) give the solubility and temperature of a saturated solution. w Solubility is on y-axis w Temperature (°C) is on x-axis

Solubility Curve

Solubility Curves w SATURATED solution is ON line or curve w UNSATURATED solution is BELOW line or curve w SUPERSATURATED solution is above line or curve

Colligative Properties w Properties that depend on the solution concentration of solute particles but NOT their identity… i. e. the addition of ANY solute will affect the property (ionic compounds usually more of an effect than molecular)

Colligative Properties examples Vapor Pressure – pressure caused by molecules that have escaped the liquid phase; nonvolatile solutes will lower the vapor pressure; the addition of a solute prevents as many water molecules from leaving

Vapor Pressure, cont’d w Volatile Substances will increase vapor pressure (volatile means that it evaporates easily – volatile substances like acetone will increase vapor pressure when mixed with water)

Freezing Point Depression w Adding a solute to water will LOWER the freezing point – w The ocean freezes at -2. 2 o. C because of the added salt w Antifreeze is added to car radiators in the winter to prevent from freezing w Electrolytes have more of an impact than non -electrolytes do

Boiling Point Elevation w The boiling point is raised when a solute is added to water w Again, electrolytes will affect this more than non-electrolytes do

Precipitation Reactions w Double Replacement reaction in which an insoluble product is formed w AC + BD AD(s) + BC(aq)