(Or Why Oil and Water don’t mix, but Sugar and Water do!)
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Transcript of (Or Why Oil and Water don’t mix, but Sugar and Water do!)
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(Or Why Oil and Water don’t mix, but Sugar and Water do!)
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• Homogeneous mixture - particles spread evenly among the particles of liquid
• The dissolved particles will not come out of solution no matter how long the covered solution is allowed to stand.
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Characteristics of Solutions, cont.• The solution is clear and
transparent . A beam of light will passing through the solution cannot be seen. – Suspended particles that are not in
solution (dust) will scatter light. Then a beam of light will be seen passing through the liquid.
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• The size of the particles in a true solution is very small. Solution particles are molecules, atoms, or ions. – Therefore, filtration cannot be used to
separate the two substances making up the solution.
• Solutions have one phase. – What are the phases of matter?
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What makes up a solution?
• SOLUTE - part of solution being dissolved; is in smaller amount
• SOLVENT - the substance that does the dissolving & is in larger amount
• What is the solute for Kool-Aid? Solvent?
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AirSodaH2 in Pt
HumidityVinegar/WaterDental
AmalgamMothball SmellSalt Water12K Gold
(Alloys)
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• Solubility -- Amount of solute that can be dissolved at a given temperature. This changes due to:– Temperature– Pressure– Nature of solute & solvent
• Miscibility -- Whether or not substances will dissolve in each other– Miscible - WILL mix/dissolve– Immiscible - will NOT mix/dissolve
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• How fast the solute dissolves in the solvent is dependent on:– Size of particles– Temperature– Stirring– Amount of solute
already dissolved
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• Substances with similar bonds dissolve into each other. – Polar & Polar
•Water and Isopropanol (Rubbing Alcohol)
– Polar & Ionic•Water and most Salts (NaCl, CaCl2, KI,
etc.)
– Nonpolar & Nonpolar •Nail Polish and Nail Polish Remover•Oil Paint and Terpentine
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Why doesn’t oil dissolve in H2O?
• Oils are non-polar molecules.
• Water is a polar molecule.
• Molecules with unlike bonds do not dissolve into each other.
Oil - No charge on the molecule
Water -Separation of
Charge
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Describe NaCl dissolving in H2O• Water is a dipole.• NaCl dissociates into
Na+ ions and Cl- ions.
• The - end of the H2O molecule is attracted to the Na+ ion in the salt crystal and pulls it into the water.
• The + end of the water is attracted to the Cl- ion.
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http://nobel.scas.bcit.ca/chem0010/unit9/9.4_solubilityionic.htm
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http://nobel.scas.bcit.ca/chem0010/unit9/9.4_solubilityionic.htm
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Concentrations of Solutions• Unsaturated -- A solution that
contains less than the maximum amount of solute that can be dissolved at that temperature.
• Saturated Solution -- A solution containing the maximum amount of solute that can be dissolved at that temperature.
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Supersaturated Solutions?
• Supersaturated -- A solution that contains more solute than would normally dissolve at that temp. Unstable!
• How can a solution be supersaturated? – Well, how can we dissolve MORE solute?– Heat!– So, heat a solution, dissolve MORE
solute, then cool it CAREFULLY.
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A formerly supersaturated solution -- a single crystal of the solute introduced will cause ALL of the excess solute to come out of solution suddenly!
http://www.chem.ufl.edu/~itl/2045/lectures/lec_i.html
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Dilution and Solutions• Dilute vs. Concentrated:
– Dilute – small amount of solute, large amount of solvent
– Concentrated – small amount of solvent, large amount of solute
• Molarity -- the measurement of the number of moles of solute per liter of solvent– M = n / V– M -- molarity– n -- number of moles– V -- total volume of solution
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Mixtures that are like Solutions, but aren’t Solutions!• Suspension
– Mixture where particles eventually settle to the bottom
– Particles are MUCH bigger than a solution. They may be visible• ex. Chocolate is suspended in hot
chocolate or chocolate milk• ex. Tiny particles of dirt (silt) are
suspended in river or pond water
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Like Solutions, but not, cont.• Colloid
– Mixture containing particles of a size between suspension and true solution
– The particles are not actually dissolved, but also not as large as a suspension’s particles.
– Particles remain dispersed (do not settle out), but not dissolved:• may appear cloudy: ex. fog, aerosols,
smoke, plain milk• may appear as something between two
phases: ex. Jell-o
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Suspension, Colloid, Solution (L to R)
Notice that the particles have settled out of the Suspension
A Colloid’s particles reflect light
A Solution’s particles DON’T reflect light - looks clear!
http://dl.clackamas.cc.or.us/ch105-03/similar.htm
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Like Solutions, but not, cont.• Emulsions
– Colloidal dispersions of liquid in liquid– Tiny particles of one liquid dispersed in
another liquid, but NOT dissolved.– These are held together by an
emulsifier:• An emulsifier causes two immiscible liquids
to mix because one end is polar and one is nonpolar.
• ex. egg in mayonnaise, soap in soapy water
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Soap Molecule
Soap molecules immersed in grease stain
Nonpolar molecule of grease
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The End!
How many solutions do you think you encounter on a daily basis?