cornell notes
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CORNELL NOTES. In the body of the notes: Take notes in class in the format that is most comfortable to you: Outline, text, shorthand, sketches, diagrams, examples Do NOT copy notes word for word think as you write rephrase abbreviate organize. Use the side to list main points - PowerPoint PPT PresentationTRANSCRIPT
CORNELL NOTESIn the body of the notes:Take notes in class in the format that is most
comfortable to you:Outline, text, shorthand, sketches, diagrams,
examplesDo NOT copy notes word for word
think as you writerephraseabbreviateorganize
Use the side to list main points
Organize ideas
Ask questions such as might be on a test or that you wonder about
Use thinking skills to question, bring ideas together, and extend them
At the bottom, summarize main ideas at appropriate intervals
SOLUTIONSA solution is a homogeneous mixture; particles are evenly distributed throughout the mixture.• Proportions may vary• Uniform ratio throughout the mixtureA liquid solution is clear. The particles are not visible, do not settle, and can not be filtered.A solution differs from a suspension in that the particles of a suspension are visible, can be filtered, and settle. A solution differs from a colloid in that the particles of a colloid exhibit Tyndall effect., yet do not settle. (TYNDALL effect: the scattering of light by particles such as headlights in fog, flashlight through Jello or dilute milk)A solution will not exhibit the Tyndall effect.
SOLUTIONS Solnshomogeneous mixtureevenly distributed particles• variable proportions• uniform ratio Liq soln clear. particles are not visible, do not settle,
and can not be filtered. Not suspensions: particles of a susp are visible, can
be filtered, and settle. Not colloids: particles of a colld show Tyndall effect.,
yet do not settle. (TYNDALL effect: the scattering of light by particles
such as headlights in fog, flashlight dilute milk) A soln will not exhibit the Tyndall effect.
SOLUTIONS Solnshomogeneous mixtureevenly distributed particles• variable proportions• uniform ratio liquid soln clear. particles are not visible, do not settle,
and can not be filtered. Not suspensions: particles of a susp are visible, can
be filtered, and settle. Not colloids: particles of a colld exhibit Tyndall
effect., yet do not settle. (TYNDALL effect: the scattering of light by particles
such as headlights in fog, flashlight dilute milk) A solution will not exhibit the Tyndall effect.
Define soln
Describe soln
Are all solns liquid?
Contrast liquid soln with susp and colloids
SOLUTIONS Solnshomogeneous mixtureevenly distributed particles• variable proportions• uniform ratio liquid soln clear. particles are not visible, do not settle,
and can not be filtered.
Not suspensions: particles of a suspension are visible, can be filtered, and settle.
Not colloids: particles of a colloid exhibit Tyndall effect., yet do not settle.
(TYNDALL effect: the scattering of light by particles such as headlights in fog, flashlight dilute milk)
A solution will not exhibit the Tyndall effect.
Define solution
Describe solution
Are all solns liquid?
Contrast liquid solution with suspensions and colloids
Solutions are homogenous mixtures with variable proportions and uniform ratios. Separate components are not visible/discernible.
Cherry Kool-aidRed powder: flavor and colorWhite crystals: sugarClear liquid: water
One substance dissolved in another◦Solute: the substance being dissolved◦Solvent: the substance that dissolves
the solute Sugar is the SOLUTE (smaller quantity) Water is the SOLVENT (larger quantity)
Types of SolutionsGas (solvent is gas)
◦ Gas into Gas: air◦ Liquid into Gas: humidity◦ Solid into Gas: air pollution
Liquid (solvent is liquid)◦ Gas into Liquid: pop◦ Liquid into Liquid: vinegar◦ Solid into Liquid: sweet tea
Solid (solvent is solid)◦ Gas into Solid: absorbent charcoal◦ Liquid into Solid: dental fillings◦ Solid into Solid: alloys of metal
The Dissolving ProcessTwo factors affect the dissolving
process: dissolution◦The constant motion of the particles
(There’s that good old kinetic molecular theory again!)
◦The polarity of the solute and solvent (Recall that polarity is when a compound has partial charges because of uneven distribution of charges)
Steps of the Dissolving Process1. Moving solvent particles cluster
around solute molecules or particles at the surface of the solid.
2. Solvent molecules pull solute off of the solid surface and into solution.
3. Moving solvent particles continue to spread solute evenly throughout the solution,
The process repeats itself as fresh layers of the solute are exposed.
1. Solvent particles cluster around solute particles at the surface.
2. Solvent particles pull solute particles away from surface, into solution.
3. Moving solute particles continue to spread solute evenly through solution.
MOLECULAR
1. Solvent particles cluster around solute particles at the surface.
2. Solvent particles pull solute particles away from surface, into solution.
3. Moving solute particles continue to spread solute evenly through solution.
IONIC
IONIC COMPOUNDSWhen an ionic substance dissolves in
water, the forces of the solvent pulling on the ions is stronger than the forces holding the ions together.
The ions separate. This is called DISSOCIATION
Because charged ions are present in an ionic solution, ionic solutions conduct electricity and are called ELECTROLYTES.
EXAMPLE: NaCl
MOLECULAR COMPOUNDSCertain polar substances form
ions when they dissolve in water. This process is called IONIZATION.
Because ions are formed, the solution conducts electricity.
These substance are also ELECTROLYTES.
EXAMPLE: HCl, HC2H3O2
MOLECULAR COMPOUNDSOther polar substances do not
ionize in water.Because ions are not formed, the
solution does not conduct electricity.
These substances that do not ionize in water and do not conduct electricity are called NON-ELECTROLYTES.
EXAMPLE: sugar
ELECTROLYTES: substances that conduct electricity when dissolved in water
Ionic substances that separate into ions (dissociate) or polar molecular substances that form ions (ionization) when dissolved conduct electricity and are called ELECTROLYTES.
ReviewA substance whose water
solutions do not conduct electricity is a non-electrolyte.◦Many covalent compounds
A substance that separates into ions (dissociates) or forms ions (ionizes) in a water solution conducts electricity and is called an electrolyte◦All ionic and some covalent
compounds
COMPOUNDS THAT DISSOLVE
IN WATER
ELECTROLYTESDO CONDUCT ELECTRICITY
IONIC COMPOUNDS DISSOCIATE
INTO IONS
SOME POLAR MOLECULAR COMPOUNDS
IONIZE
NON-ELECTROLYTES
DO NOT CONDUCT
ELECTRICITY
OTHER POLAR MOLECULAR COMPOUNDS
DISSOLVE WITH NO FORMATION OF
IONS
Factors Solid in Liquid
Gas in Liquid
TEMPERATURE Temp > Rate >
Temp > Rate <
AGITATION Agitation > Rate >
Agitation > Rate <
SIZE OF PARTICLES
Size < (surface area
>) Rate >
NA
PRESSURE NA Pressure > Rate >
WHY? The solute particles are
less energetic than solvent
The solute particles are
more energetic than
solvent
FACTORS THAT AFFECT THE RATE OF DISSOLUTION
Think BIGRecall the Pop and Mentos experiment!
The pop “explodes” because the dissolved gas rapidly leaves the solution because the
candy gives it surfaces to collect on (nucleation sites).
Particles in SolutionsSolvents with non-polar
molecules dissolve non-polar substances◦Oil, grease, dry cleaning fluid, paint,
turpentineSolvents with polar molecules
dissolve polar substances◦Water dissolves sugar, ionic
compounds
LIKE DISSOLVES LIKE
TermsSoluble: capable of being
dissolved in a particular solventInsoluble: incapable of being
dissolved in a particular solvent
Miscible: liquids that dissolve freely in any proportion
Immiscible: liquids that are not soluble in each other
Detergents and emulsifiersGrease is non-polarWater is polar
DETERGENT has ◦A non-polar end that dissolves the
grease◦A polar end that dissolves in the
water to rinse it away NONPOLAR DETERGENT
POLARGREASE WATER
CRAFTY CHEMISTRYArtists use physical properties to create inspiring beauty!
ART and SCIENCE
SolubilityThere are limits to the amount of
solute that will dissolve in a given amount of solvent at a given temperature
There are some general terms:◦Unsaturated◦Saturated◦Super-saturated
Unsaturateda solution that can dissolve more
of a given solute at a certain temperature◦A crystal of solute added to an
unsaturated solution will dissolve When you add a second spoon of sugar
to your cup of tea, it dissolves. The tea was an unsaturated solution.
Saturateda solution that has dissolved all of the
solute that it can at a certain temperature◦ A crystal of solute added to a saturated
solution will drop to the bottom, un-dissolved. When you add three spoons of sugar to your tea,
some sugar drops to the bottom, undissolved. It is a saturated solution.
DYNAMIC EQUILIBRIUM exists: ◦ changing but balanced.◦ Some solid dissolves, but as some
dissolves, some re-crystallizes
Super-saturatedan unstable solution that contains
more solute than a saturated solution at a certain temperature◦ A crystal of solute added to a super-
saturated solution will cause crystallization. So will any disruption of the unstable solution.
◦ Make a saturated solution at an elevated temperature and cool it slowly. At the lower temperature, the solute will remain dissolved in an unstable situation. If disrupted, the solute crystallizes. Hot-packs and rock candy
SOLUBILITY CURVE
Max g of solute that will dissolve in 100 g of solvent at a given temperature
Solubility + Gas Laws = Safe SCUBAScience of Diving
Concentration: the amount of solute in a given amount of solvent or solutionDilute: a relatively small amount
of solute in a relatively large amount of solvent
Concentrated: a relatively large amount of solute in a relatively small amount of solvent
We can do better!
Percent by volumemL of solute /100 mL of solution
Percent by massg of solute/100 mL of solution
PPM and PPBx/1,000,000x/1,000,000,000
Serial dilutions are often used◦1x, 10x, 100x, 1000x, etc.
Mass per volumeg solute/1000 mL solution
MolarityM = mol solute/liter of solution
Chemists use this because it lets us work concentration into stoichiometry problems
SEE EXAMPLE PROBLEMS
Molalitym = mol solute/kg of solvent
Chemists sometimes use this because volume of liquids changes with temperature. Soon, we will be studying the effect of concentration as temperature changes.
SEE EXAMPLE PROBLEMS
Dilutions: a concentrated solution is diluted by adding more solvent to get the desired concentration. M1V1 = M2V2
Moles before dilution = Moles after
dilution◦M = molarity = mol/L◦V = volume = L◦M x V = mol/L x L = # mol of solute
Dilutions: a concentrated solution is diluted by adding more solvent to get the desired concentration.
The # of moles before dilution is equal to the # of moles after dilution. The same # of moles is present in more solvent. The concentration (M, molarity) changes, the volume (V) changes, but not the # of moles of solute (M x V). ◦ Volume units may vary from L, but must be consistent
within problem.So, M1V1 = M2V2
SEE EXAMPLE PROBLEMS