(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?

Air Soda H 2 in Pt Humidity Vinegar/Water Dental Amalgam Mothball Smell Salt Water 12K 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, CaCl 2, KI, etc.) –Nonpolar & Nonpolar Nail Polish and Nail Polish Remover Oil Paint and Terpentine

Why doesn’t oil dissolve in H 2 O? 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 H 2 O Water is a dipole. NaCl dissociates into Na+ ions and Cl- ions. The - end of the H 2 O 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.

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!

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!

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?