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Solutions! Classification of Matter Matter Pure Substances Elements Compounds Mixtures Homogeneous Mixtures Heterogeneous Mixtures Mixtures homogeneous: • will not separate heterogeneous: • settles upon standing • small particles • variable particle sizes – evenly distributed – too small to be seen – can’t be sorted or trapped by filter – won’t scatter light – uneven distribution – visibly different regions – can be separated depending on particle sizes – scatters light Solution homogeneous mixture of 2 or more substances in a single physical state (phase) Parts of a Solution • solute = substance being dissolved • solvent = dispersing medium substance being dissolved into Can you identify the solute and solvent in each picture? solute = ? solvent = ? hints to identify solute & solvent • solute: –substance that changes phase –substance that have less of • solvent: –substance that maintains phase –substance that have more of Aqueous Solutions • water is solvent • transition metals form brightly colored solutions solutions occur in all 3 phases solute solvent example gas gas air liquid gas water vapor in air solid gas SO2(s) in air - smog gas liquid CO2(g) in water (soda) liquid liquid antifreeze(l) in water in car radiator solid liquid salt water gas solid H2(g) in palladium metal liquid solid dental amalagum fillings: Hg (l) in Au(s)/Ag(s) solid solid alloys: Brass, etc. gas in a liquid: CO2 in and out of water bubbles mean it’s a mixture not a solution! Concentration of Solutions Concentration • measurement that describes how much solute in given amount of solvent or solution • express concentration using many, many different units – pick the unit according to task at hand Percent • by mass OR • by volume % = part x whole 100 Twists in Word Problems • sometimes ask for part or whole, not percent • sometimes give volume/mass of solution • sometimes give volume/mass of solvent and volume/mass of solute mass solution = mass solute + mass solvent ppm (parts per million) • used when solute is present in very small amounts (Regents board doesn’t quite follow this rule) ppm (parts per million) ppm = grams solute x grams solution 1,000,000 • ppm is ratio between mass solute & mass soln • similar to % except the whole is 1,000,000 instead of 100 About 0.0043 g of O2 can be dissolved in 100 mL of water at 20oC. Express in ppm. [memorize: 1 mL water has mass of 1 g] • ppm = 0.0043g x 100.0043g = 43 ppm 1,000,000 CO2 gas has solubility of 0.0972 g/100 g water at 40oC. Express in parts per million. ppm = 0.0972 g solute x 100.0972 g solution = 971 ppm 1,000,000 What is the concentration in ppm of a solution with 30.0 g NaNO3 in 70.0 g water? ppm = 30.0 g NaNO3 100.0 g solution x 1,000,000 = 300,000 = 3.0 X 105 ppm How many grams of KOH are needed to be dissolved in water to make 2000.0 grams of a 10.0 ppm solution? 10 ppm = ? grams KOH X 1,000,000 2000.0 g solution ? = 0.02 grams KOH