(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!)
(Or Why Oil and Water don’t mix, but Sugar and Water do!)
• 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.
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.
• 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?
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?
AirSodaH2 in Pt
HumidityVinegar/WaterDental
AmalgamMothball SmellSalt Water12K Gold
(Alloys)
• 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
• How fast the solute dissolves in the solvent is dependent on:– Size of particles– Temperature– Stirring– Amount of solute
already dissolved
• 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
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
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.
http://nobel.scas.bcit.ca/chem0010/unit9/9.4_solubilityionic.htm
http://nobel.scas.bcit.ca/chem0010/unit9/9.4_solubilityionic.htm
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.
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.
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
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
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
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
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
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
Soap Molecule
Soap molecules immersed in grease stain
Nonpolar molecule of grease
The End!
How many solutions do you think you encounter on a daily basis?