chemistry day 62 · do-now: “solutions cn b” 1. write down today’s flt: i will be able to...

Chemistry Day 62 Wednesday, March 25th, 2020

Do-Now: “Solutions CN B” 1. Write down today’s FLT: I will be able to

identify the factors that determine the rate at which a solute dissolves by completing Solutions CN B

2. Why is water able to dissolve ionic compounds? Be as specific as possible.

3.  Is ice more or less dense than liquid or gas water?

4. Define the word “solution”. 5. Explain if a glass of saltwater is a solution

or not.

Planner: •  Study! I recommend re-doing practice

problems from notes and quizzes. • Write your name on today’s date in your

planner and send it to me on remind for extra dojos

Table of Contents #2: 14.  Solutions CN B 15.  Solutions WS B

FLT •  I will be able to identify the factors that

determine the rate at which a solute dissolves by completing Solutions CN B

Standard HS-PS1-3:Planandconductaninvestigationtogatherevidencetocomparethestructureofsubstancesatthebulkscaletoinferthestrengthofelectricalforcesbetweenparticles.

Recall: Water is Polar

Recall: Like Dissolves Like •  Polar/chargedmoleculesdissolveotherpolar/chargedmolecules

• Nonpolarmoleculesdissolveothernonpolarmolecules

• …So,what’sthedifference?

Solutions CN B: Properties of Solutions

Recall

Solvents and Solutes •  Solution=homogeneousmixtureofsolvent+solute.

Homogeneous vs. Heterogeneous

Mixtures • Mixturesarecombinationsoftwoormoredistinctsubstances

• Mostnaturalsubstancesexistasmixtures– Ex/Evenwatercontainsimpurities,andthereforeexistsasamixture

Homogeneous vs. Heterogeneous • Homo=same,Hetero=different• Homogeneousmixture=uniformthroughout(solutions)– Ex/Saltwater,Air

Homogeneous vs. Heterogeneous • Homo=same,Hetero=different• Heterogeneousmixture=non-uniformthroughout(unevenlydistributed)– Ex/Saltwaterwithsandinit

Non-Homogeneous Mixtures

Mixtures that are NOT Solutions: •  Suspensions=mixturesw/largeparticlesthatslowlysettle(ex/sandywater)– Particlesofasuspensionaregreaterindiameterthan1000nm.

– Canbeseparatedbyfiltering

Mixtures that are NOT Solutions: •  Colloids=heterogeneousmixturesw/mediumsizeparticles

•  Betweenthesizeofsuspensionsandtruesolutions(1-1000nm)

•  Ex/Blood,milk

Dissolution

Dissolution •  Recall-The“nature”(polarity,orcomposition)ofthesoluteandthesolventwilldetermine…– Whetherasubstancewilldissolve– Howmuchwilldissolve

Dissolution •  Youareaddingsugartoyourtea,butyounoticethatit’snotdissolving.Whatdoyoudo?

Dissolution • Whichwoulddissolvefaster–asugarcube,orgranulatedsugar?

Dissolution •  Ifwewanttoincreasetherateofdissolution,weneedtoincreasecontactbetweenthesoluteandsolventparticles

•  Howcanwedothat?•  FactorsAffectingtheRateofDissolution:

Dissolution 1.  Stirring/Agitation

•  increases contact between solute & solvent particles

Dissolution 2.  Surface Area (of solute)

•  Smaller pieces = more SA = more contact between solute and solvent

Dissolution 3.  Temperature

•  High T = Greater avg. KE = Particles move faster = more contact between solute and solvent

•  High T can also increase the total amount of solute that will dissolve!

Saturation

Saturation •  Solubility=maxamtofsubstancethat

willdissolveataspecifictemperature.•  Units=gsolute/100gsolvent

Saturation •  UnsaturatedSoln’=Canstilldissolve

moresolute–  Ex/Solutecompletelydisappears

Saturation •  SaturatedSoln’=Containsthemaxamt

ofsolutedissolved.

Saturation •  SupersaturatedSoln’=Containsmore

thanittheoreticallycandissolve

Saturation and Equilibrium

Solute is dissolving

More solute is dissolving, but some is crystallizing

Saturation equilibrium established

Solubility

Solubility •  éTemperature:

–  ésolubilityforsolidsandliquids

•  Ex/Sugarintea–  êsolubilityfor

gases•  Ex/Gasescapes

fromliquidwaterwhenboiling

Solubility •  Whataboutpressure?•  Henry’sLaw=Solubilityofagasina

liquidisdirectlyproportionaltothePofthegasabovetheliquid

– Ex/ When you remove the cap of a bottle of soda, you release pressure, and then the gas starts to escape

Solubility •  Ofcourse,there’sanequation

Miscibility

Liquids •  Miscible=Whentwoliquidscanmix/

dissolve–  Waterandantifreezemixanddissolve

Liquids •  Someliquidsareonlypartiallymiscible

–  Ex/Waterandether

Liquids •  Immiscible=Cannotmix/Dissolve

–  Ex/Oilandvinegar

Pair-Share-Respond 1.   Listthreefactorsthataffecttherateof

dissolution2.   Explainhoweachofthosethreefactors

affectstherate3.   Youaddasolute,andnoticethatitall

disappearsinthesolvent.Isthissolutionsaturated,unsaturated,orsupersaturated?

4.   Ifyouincreasethetemperature,willasoliddissolvefasterorslower?

5.   Ifyouincreasethepressure,willagasdissolvefasterorslower?

HW •  SolutionsWSB•  Study