Solutions!Solutions!

Classification of MatterClassification of Matter

MatterMatter

PureSubstances

Mixtures

HomogeneousHomogeneousMixturesMixtures

HeterogeneousHeterogeneousMixturesMixtures

ElementsElements CompoundsCompounds

Heterogeneous MixturesHeterogeneous Mixtures

• See See visibly different regionsvisibly different regions– GraniteGranite

– DirtDirt

– CerealsCereals

– Oil & VinegarOil & Vinegar

• See a See a boundaryboundary– Ice cube in waterIce cube in water

Homogeneous MixturesHomogeneous Mixtures

• ParticlesParticles very smallvery small – on atomic scale – on atomic scale– Can’t see particles– Can’t sort particles– Can’t get trapped by filter– Can’t scatter light

• Particles Particles evenly distributedevenly distributed• Particles Particles do not separatedo not separate

CuSO4(aq)

Which is a solution & how do you know?Which is a solution & how do you know?

SolutionSolution

Homogeneous mixture of 2 or Homogeneous mixture of 2 or more substances in a single more substances in a single physical statephysical state (phase) (phase)

Parts of a SolutionParts of a Solution

• SoluteSolute = dissolved substance

• SolventSolvent = dispersing medium

Identify the solute Identify the solute and solvent in each and solvent in each picturepicture

Solute = ? Solvent = ?Solute = ? Solvent = ?

Hints to identify solute & solventHints to identify solute & solvent

• SoluteSolute: changes phase = substance have less of

• SolvenSolvent: maintains phase

= substance have most of

Aqueous SolutionsAqueous Solutions• WaterWater is

solvent

• Transition Transition metalsmetals form brightly colored solutions

Solutions occur in all 3 phases!Solutions occur in all 3 phases!

Alloys: Brass, etc.Alloys: Brass, etc.SolidSolidSolidSolid

Fillings: Hg in AgFillings: Hg in AgSolidSolidLiquidLiquidHH22 in Pd metal in Pd metalSolidSolidGasGas

Salt waterSalt waterLiquidLiquidSolid Solid

Antifreeze in radiatorAntifreeze in radiatorLiquidLiquidLiquidLiquid

Seltzer WaterSeltzer WaterLiquidLiquidGasGas

MothballsMothballsGasGasSolidSolid

Water Vapor in AirWater Vapor in AirGasGasLiquidLiquid

AirAirGasGasGasGas

ExampleSolventSolute

Gas dissolved in a solidGas dissolved in a solid

COCO22 in and out of water in and out of water

Bubbles mean it’s a mixture not a solution!Bubbles mean it’s a mixture not a solution!

Alloys

Alloys

SolubleSoluble

SolubleSoluble – capable of being dissolved

A substance that dissolves in another substance is solublesoluble

in that substance

InsolubleInsoluble

A substance that does not dissolve in another substance

Amounts that can dissolveAmounts that can dissolve

• Solubility Solubility = maximum amount of substance that will dissolve in given amount of another substance

• LIMITSLIMITS to amounts of most liquid/solid solutes that will dissolve in given solvent

• TemperatureTemperature and pressurepressure affect solubility

Factors that affect the rate of dissolvingFactors that affect the rate of dissolving

• RateRate of dissolving is of dissolving is different different from from amountamount that will dissolve! that will dissolve!

• Rate is Rate is how fasthow fast –factors influence rate of dissolving:factors influence rate of dissolving:

• TemperatureTemperature

• Stirring or Stirring or AgitationAgitation

• Surface Area of SoluteSurface Area of Solute

• Amount of soluteAmount of solute already dissolved already dissolved

DissolvingDissolving

• Dissolving is Dissolving is physical changephysical change

• All physical & chemical changes All physical & chemical changes are accompanied by changes in are accompanied by changes in energyenergy

Equations for DissolvingEquations for Dissolving

CC66HH1212OO66(s) + H(s) + H22O(l)O(l) C C66HH1212OO66(aq)(aq)

NaCl(s)+HNaCl(s)+H22O(l) O(l) Na Na+1+1(aq) + Cl(aq) + Cl-1-1(aq) (aq)

source

Covalent substances dissolve to Covalent substances dissolve to produce molecules in solutionproduce molecules in solution

Ionic substances dissolve to produce Ionic substances dissolve to produce ions in solutionions in solution

SolvationSolvation

• Interaction between solvent molecules and Interaction between solvent molecules and solute particlessolute particles– Solute particles surrounded by solvent particles in Solute particles surrounded by solvent particles in

dissolving process dissolving process

• Solute particlesSolute particles may be ions, polar molecules, may be ions, polar molecules, or nonpolar moleculesor nonpolar molecules

• Solvent moleculesSolvent molecules may be polar or nonpolar may be polar or nonpolar

HydrationHydration

Specific name for Specific name for solvent-solute solvent-solute interactioninteraction when when solvent is watersolvent is water

Hydration of Hydration of chloride ion chloride ion

Also called: Also called: molecule-ion molecule-ion interactioninteraction

Solute-solvent interactionSolute-solvent interactionmust be must be greatergreater than: than:

interaction between interaction between solute particlessolute particles

for for dissolving to occurdissolving to occur

Molecule-ion interaction

Solvation in different systems.

SolubilitySolubility

• Amount solute that will dissolve in specific Amount solute that will dissolve in specific solvent at givensolvent at given TEMPERATURE and TEMPERATURE and PRESSUREPRESSURE

• Amount can be determined experimentallyAmount can be determined experimentally

• Units: Units: grams solute per 100 grams solventgrams solute per 100 grams solvent

Solubility Curves of Selected SOLIDSSolubility Curves of Selected SOLIDS

SolubilitySolubility traces traces for for mostmost but not but not all all solidssolids have have ((+)’ve slopes;+)’ve slopes;

The hotter the The hotter the solvent, the solvent, the more solute more solute dissolvesdissolves

Solubility Curves of Selected GASESSolubility Curves of Selected GASES

SolubilitySolubility traces for traces for allall gases havegases have(–)’ve slopes(–)’ve slopes

Why do fish like cold water?Why do fish like cold water?

Why do you see Why do you see bubbles form on bubbles form on the side of the the side of the beaker as the beaker as the water warms up? water warms up? (Note: it’s not hot (Note: it’s not hot enough to boil)enough to boil)

Vocabulary InterludeVocabulary Interlude

• MiscibleMiscible: two liquids that WILL MIX together in any amounts

– Water and ethanol are miscible in all Water and ethanol are miscible in all proportionsproportions

• ImmiscibleImmiscible: Liquids that will NOT MIX– Oil and water are immiscibleOil and water are immiscible

Oil & HOil & H22O are immiscibleO are immiscible

Types of Solutions

Matter

Pure Substances Mixtures

HomogeneousMixtures =Solutions

Heterogeneous

MixturesElements Compounds

Conduct current

Nonconductor

Electricity

• What do you need to conduct What do you need to conduct electricity?electricity?

Mobile, charged particles!!!!Mobile, charged particles!!!!

Vocabulary InterludeVocabulary Interlude

• ElectrolyteElectrolyte: • substance that dissolves in water to form

solution that conducts electricity • ions in solution

• NonelectrolyteNonelectrolyte: • substance that dissolves in water to form

solution that does not conduct electricity • neutral molecules in solution

Electrolyte vs. NonelectrolyteElectrolyte vs. Nonelectrolyte

Which solution conducts a current?

Dilute vs. ConcentratedDilute vs. Concentrated

Tells relative amount of solute in solvent

• ConcentratedConcentrated

–large amounts of solute

• DiluteDilute

–small amounts of solute

Which solution is most dilute?

The most concentrated?

How do youknow?

The stronger the color, the more concentrated the solution

Which solution is more concentrated? More dilute?

What can you say about the # of solute of solute particlesparticles in pictures b and c?

It’s the same!It’s the same!

Unsaturated SolutionUnsaturated Solution

LessLess solute than maximum amount that will dissolve at given temperature and pressure

Saturated SolutionSaturated Solution

• No more solute will dissolveNo more solute will dissolve at at given temperature & pressuregiven temperature & pressure

• SolubilitySolubility = amount of solute = amount of solute required to form a saturated required to form a saturated solutionsolution

The solution is saturated when the solute The solution is saturated when the solute stops dissolvingstops dissolving

Dynamic Equilibrium = Saturated SolutionDynamic Equilibrium = Saturated Solution

Microscopic level: Rate of dissolving = Rate of dissolving = Rate of Rate of recrystallizationrecrystallization

Macroscopic level: No apparent changeNo apparent change

Supersaturated SolutionSupersaturated Solution

• Contains moremore solute than saturated solution–VERY unstable–have to be clever to make these

(need to use heat)

Testing for saturation:Testing for saturation:

Toss crystal of solute into solution and see what happens

3 possible results:3 possible results:

• Crystal dissolves:Crystal dissolves:

• Crystal sinksCrystal sinks to bottom of solution: to bottom of solution:

• Bam! Suddenly have Bam! Suddenly have lots of solid solutelots of solid solute in in beaker:beaker:

Unsaturated solution

Saturated solution

Supersaturated solution

What kind of solution was this?What kind of solution was this?

How do terms saturated, unsaturated & How do terms saturated, unsaturated & supersaturated fit in with the solubility curves?supersaturated fit in with the solubility curves?

• Saturated solutions have maximum solute that will dissolve at given temperature – Any point on trace lines represent saturated

solutions

• All points above trace lines represent supersaturated solutions

• All points below trace lines represent unsaturated solutions

AB

CD

Characterize points Characterize points A, B, C, D with respect A, B, C, D with respect to the KNOto the KNO33 trace trace using the terms using the terms dilute & concentrated, dilute & concentrated, saturated, unsaturated, saturated, unsaturated, or supersaturatedor supersaturated

A,C = concentrated & supersaturated

B,D = dilute & unsaturated

Summary ofSummary of Dissolving Dissolving

• Occurs atOccurs at surfacesurface of solid of solid

• Involves Involves interaction betweeninteraction between solute solute andand solventsolvent

• Interaction is Interaction is called “solvation”called “solvation”– If water is solvent, interaction is called If water is solvent, interaction is called

“hydration”“hydration”

• Involves Involves changes in energychanges in energy

Solubility InformationSolubility Information

• Often presented in graphs

• Graph show number grams of substance that can dissolve in water between 0oC and 100oC

• Trace line represents saturated solution– above trace line represents supersaturated solutions– below trace line represents unsaturated solutions

Solubility GraphsSolubility Graphs

• Traces: have positive or negative slopes

• MostMost solids solids have positive slope– the hotter the water, the more solute dissolves– The colder the water, the less solute dissolves

• AllAll gases gases have negative slope – the hotter the water, the less gas dissolves– The colder the water, the more gas dissolves