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07/16/96
SOLUTIONS *

2. Solutions Solution – a homogeneous mixture of pure substances
The SOLVENT is the medium in which the SOLUTES are dissolved. (The solvent is usually the most abundant substance.)
Example:
Solution: Salt Water
Solute: Salt
Solvent: Water

3. READ ONLY SECTION: HOW DO SUBSTANCES DISSOLVE?
“According to the kinetic theory, the water molecules in each glass of tea are always moving. Some moving water molecules collide with sugar crystals. When this happens, energy is transferred to the sugar molecules at the surface of the crystal.” (Holt, p. 192)

4. The process of dissolution is favored by:
A decrease in the energy of the system (exothermic)
An increase in the disorder of the system (entropy)

5. Liquids Dissolving in Liquids
Liquids that are soluble in one another (“mix”) are MISCIBLE.
“LIKE dissolves LIKE”
POLAR liquids are generally soluble in other POLAR liquids.
NONPOLAR liquids are generally soluble in other NONPOLAR liquids.

6. Factors affecting rate of dissolution:
Surface area / particle size
Greater surface area, faster it dissolves
Temperature
Most solids dissolve higher temps
Agitation
Stirring/shaking will speed up dissolution

7. Saturation Unsaturated solution – is able to dissolve more solute
Saturated solution – has dissolved the maximum amount of solute
Supersaturated solution – has dissolved excess solute (at a higher temperature). Solid crystals generally form when this solution is cooled.

8. SOLUBILITY
Solubility = the amount of solute that will dissolve in a given amount of solvent

9. Factors Affecting Solubility
The nature of the solute and solvent: different substances have different solubilities
Temperature: many solids substances become more soluble as the temp of a solvent increases; however, gases are less soluble in liquids at higher temps.
Pressure: Only affects the solubility of gases. As pressure increases, the solubility of gases increases.