What Are Solutions?

(more than just answers to chemistry questions…) Ms. Besal 2/30-31/2006

In this corner… • Mixture: A

mixture

is a chemical substance which is a

homogeneous

or

heterogeneous

association without chemical bonding of elements and/or compounds in varying proportions and that retain their own individual properties and makeup.

• Remember that you “can see the parts” http://en.wikipedia.org/wiki/Homogeneous_mixture

And in this corner… • Solution: A

solution

is a

homogenous

mixture of two or more substances in a single physical state.

• Remember that you “cannot see the parts” Zado, B. (2005). “Solutions”

How do we put it all together?

mixtures heterogeneous homogeneous Aqueous solutions electrolytes solutions tinctures alloys amalgams

What makes up a solution?

• Solute: the substance being dissolved • Solvent: the substance doing the dissolving Name the solute and solvent: solution solute(s) Ocean water salt solvent water Coca-cola Sugar, carbon dioxide Humid air Water vapor water air

S o l u t e Examples of solutions Gas Gas

Oxygen and other gases in nitrogen (air)

Liquid

Water vapor in air (humidity)

Solid

The odor of a solid results from molecules of that solid being dissolved in the air

Solvent Liquid Solid

Carbon dioxide in water (carbonated water) Hydrogen dissolves rather well in metals; platinum has been studied as a storage medium Ethanol (common alcohol) in water; various hydrocarbons in each other (petroleum) Sucrose (table sugar) in water; sodium chloride (table salt) in water Water in activated charcoal; moisture in wood Steel, brass, other metal alloys Adapted from http://en.wikipedia.org/wiki/Solution

What types of solutions are there?

•Aqueous solutions (aq): solutions in which water is the solvent •Electrolytes: specific aqueous solutions in which the solute dissolves to form ions.

•Tinctures: solutions in which alcohol is the solvent •Alloys: solid solution of two or more metals •Amalgams: specific alloys in which one of the metals is mercury

You keep using that word… I do not think it means what you think it means.

Image from: http://us.movies1.yimg.com

You keep using that word…

What do we mean by “dissolve”?

I do not think it means what you think it means.

What does “dissolve” mean?

1.

To pass into solution.

2.

To break up or disperse.

3.

To become disintegrated; disappear.

4.

To be overcome emotionally or psychologically: I dissolved into helpless laughter.

5.

To lose clarity or definition; fade away.

6.

To shift shots in a motion-picture film or videotape by having one shot fade out while the next appears behind it and grows clearer as the first one dims.

http://www.thefreedictionary.com

What happens when salt dissolves in water?

• Like the definition suggests, salt passes into solution . The components break up or disperse into water. As a result, the salt crystal structure becomes disintegrated , and we see the salt disappear .

Double, Double, Toil and Trouble… • What can happen when we mix two liquids together?

Either they mix, or they don’t!

• If two liquids mix well together, and one dissolves in the other, we call them miscible (think “mixable”) • If two liquids do not mix well together, and they separate, we call them immiscible (think “unmixable”)

Like Oil & Water… • How do we know that two liquids will be miscible or immiscible?

• • Rule of thumb: “Like dissolves Like” – Polar solutes will dissolve in polar solvents – Nonpolar solutes will dissolve in nonpolar solvents.

Water is the “universal solvent”

…And never the two shall meet?

• How can we mix polar and nonpolar molecules into solutions? Can it be done?

• We use emulsifiers – agents that have both polar and nonpolar ends to join the two unlike molecules together – Creates an emulsion: A suspension of small globules of one liquid in a second liquid with which the first will not mix

Kitchen Khemistry!

A Recipe for Mayonnaise • • • • • •

6 Teaspoons (Real Lemon Brand) Lemon Juice

Water based – polar molecules

3 cups soybean oil (sold as "vegetable" oil)

Oil – nonpolar molecules

4 Jumbo Egg Yolks (separate and discard the whites)

A source of Lecithin – an emulsifier!

2 Teaspoons Onion Powder 1 Teaspoon Salt 1 Teaspoon Sugar or 1/2 packet of Splenda

http://www.afn.org/~poultry/recipes/mayo.htm

What use are emulsifiers?

Images from: http://www.emulsifiers.org/index.php

How can Solubility be changed?

•Surface area of the solute: More surface area = faster dissolving •Stirring: More motion = faster dissolving •Temperature: Higher temperature = faster dissolving •Pressure Higher pressure = faster dissolving