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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 withoutchemicalbonding 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”
mixtures homogeneous heterogeneous solutions Aqueous solutions alloys amalgams electrolytes tinctures How do we put it all together?
solution solute(s) solvent Ocean water Coca-cola Humid air What makes up a solution? • Solute: the substance being dissolved • Solvent: the substance doing the dissolving Name the solute and solvent: salt water Sugar, carbon dioxide water Water vapor air
Examples of solutions Solvent Gas Liquid Solid Gas Oxygen and other gases in nitrogen (air) Carbon dioxide in water (carbonated water) Hydrogen dissolves rather well in metals; platinum has been studied as a storage medium Liquid Water vapor in air (humidity) Ethanol (common alcohol) in water; various hydrocarbons in each other (petroleum) Water in activated charcoal; moisture in wood Solid The odor of a solid results from molecules of that solid being dissolved in the air Sucrose (table sugar) in water; sodium chloride (table salt) in water Steel, brass, other metal alloys Solute 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 • 3 cups soybean oil (sold as "vegetable" oil) • 4 Jumbo Egg Yolks (separate and discard the whites) • 2 Teaspoons Onion Powder • 1 Teaspoon Salt • 1 Teaspoon Sugar or 1/2 packet of Splenda Water based – polar molecules Oil – nonpolar molecules A source of Lecithin – an emulsifier! 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