(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?