Solutions

Solutes and SolubilityLink to a set of 9 quick lessons about solutes and solubility:http://www.middleschoolchemistry.com/multimedia/chapter5/lesson1

Classification of MatterClassify according to 4 states of matter

Classify by the units they are made ofElementsMatter is made up of atomsif all atoms in a sample have same identity, that matter is an element. ExamplesAl

CuAg

CompoundsMade from atoms of 2 or more elements that are combined chemically (atoms are bonded together)

H2 + O (hydrogen and oxygen)

Makes H2O (water)

Na + Cl (sodium and chlorine)NaCl saltMoleculesMade of 2 or more atoms that are combined chemically (atoms are bonded together)The atoms can be the same or different elementsMoleculesCompounds are always moleculesElements may be individual atoms or they can be molecules H2, O2, N2 are all diatomic elementsS8 is a molecule of 8 sulfur atomsChemical FormulasUse symbols and numbers to represent the elements found in a substance and the number of each of those elements present in the substanceC6H12O6 is the formula for glucose

Wrap-upSubstance: an element or compoundcant be reduced to more basic components by physical processesMixturesMaterial made up of 2 or more substances that can be separated by physical means.Each substance in a mixture keeps its own properties and identity

NaCl H2O

Salt waterMixtures contdDont always contain the same amounts of the different substances that make them up

Heterogeneous mixtureDifferent materials can be easily distinguishedNot uniformly mixedExamplesGraniteConcreteInside of your locker or backpack

SolutionsHomogeneous mixtureTwo or more substances are uniformly mixed togetherSolution particles never settle to bottom of containerRemain constantly and uniformly mixedTypes of solutionsSolutions are classified as solid, liquid, or gas depending on their final stateSolution termsSolute: substance being dissolved, less than 50% of a solutionSolvent: substance dissolving the solute, present in largest amountAir: 78% N, 21% O, 1% ArSolvent of air?Sterling silver: 92.5% Ag, 7.5% Cu. Solvent?Alloy a solution of a metal and another element (usually another metal)Ex.: brass (copper and zinc); bronze (copper and tin); cast iron (iron and carbon)Solids dissolving in liquidsDissolving of a solid in a liquid occurs at the surface of the solidSolutes dissolve from the outside to the center

The more surface there is, the faster something dissolvesA large block has less surface available (less surface area) than the same block broken into pieces

As large blocks are broken down into smaller pieces, the total surface area increases.

Animations of salt dissolving in waterhttp://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/thermochem/solutionSalt.html animation of salt dissolving in waterhttp://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf another animation of salt dissolving in water

Rate of DissolvingRate of solubility depends on how the solute is dissolvedgrams of solute/minStirring speeds up dissolving brings more fresh solvent into contact with more solute, also moves solute particles around in the solventStirring adds kinetic energy to a solution and helps solvent and solute particles collideGrinding a solute speeds dissolving of solid in liquid - large crystals become small ones and solvent has more surface area to work onIncreasing the temperature of solvent increases rate at which most solids dissolve - increasing temp speeds up action of molecules of the solvent and the solute

SolubilityPhysical property of matter that relates to the ability of a solute to dissolve in a solventA measure of how easily or how quickly a solute dissolves in a solventPhysical properties: Rate of SolubilityRate of solubility =mass of solute dissolved/time to dissolveTo calculate the rate of solubility divide the mass of the solute by the time it takes to dissolveRate of solubility units: g/min or g/secPhysical properties: Rate of SolubilityRate of solubility is affected by temperature and stirringRate of solubility is a property of a substanceThere are tables of solubility rates for various substancesMiscibilityA measure of how easily or how quickly a liquid solute dissolves in a liquid solventWater and oil are immiscible (they dont dissolve in each other)ConcentrationA measure of the amount of one substance in a specific volume of another substance.Concentration units: g/mLEx. Grams of solute per mL of solventConcentrationA solution that has 20 g of solute dissolved in 100 mL of solvent is more concentrated than a solution that has 8 g of solute dissolved in 100 mL of solventTypes of solutions based on amt. of solute dissolvedSaturated solution - solution that has dissolved all the solute it normally can hold at a given temperatureIf you heat the mixture to a higher temp, more solute can dissolve - as temp. increases, amt. of solute that can dissolve increasesUnsaturated solution - any solution that can dissolve more solute at a given temp.Each time a saturated solution is heated to a higher temp, it may become unsaturated NaCl(s) Na+(aq) + Cl-(aq)

Saturation point is 36g/100mL or 0.36g/mLSupersaturated solution - contains more solute than a saturated one has at that temperatureThis kind of solution is unstable - when a small crystal of the solute is added to a supersaturated solution, excess solute quickly crystallizes outSaturation pointPoint where no more solute will dissolve in a solutionA concentration above which the solute will no longer dissolve in the solvent, the solution is saturated and cant take any moreSummaryAdd a solute crystal to solution:If crystal dissolves, solution is unsaturatedIf crystal doesnt dissolve, solution is saturated (crystal just sinks to the bottom of the container)If additional solute comes out, solution is supersaturated