2. Solutions
• A solution is a homogeneous mixture of at least
two different compounds
• A solvent is any substance that has other
substances dissolved in it
• Solutes are substances that are dissolved in the
solvent
3. Solutions
• Liquids that dissolve easily in one another are
called miscible with each other
▫ Example: water and ethanol
• Liquids that do not dissolve easily in one another
are called immiscible
▫ Example: water and oil
4. • In an aqueous solution water is the solvent
▫ Water is also called a ‘universal solvent’
• In a saturated solution no more solute will
dissolve
• An unsaturated solution is not saturated (you
can dissolve more solute)
• Super saturated solution: a solution that
contains more dissolved solute than a saturated
solution at the same temperature and pressure.
5. Why Do Solutions Form?
3 forces must be considered
1. Forces that attract particles of the solute to each
other.
2. Forces that attract particles of solute to the
solvent
3.Forces that attract particles of solvent to each
other.
2 ≥ 1 and 3
8. Solubility
• Solubility is a measure of how much solute will
dissolve in a given amount of solvent at a
particular temperature
• For (most) solids:
▫ Solubility ↑ with Temperature
• For (most) gasses:
▫ Solubility ↓ as Temperature ↑
▫ Solubility ↓ as Pressure ↓
9. Rate of Dissolving
• In general, the rate of dissolving increases with:
▫ Temperature
▫ Stirring or swirling
▫ Smaller particle size (eg, crushing a solid
into a powder)
10. Dissolving a Solid in a Liquid
• Dissolving is not a chemical reaction
• Step 1:
▫ Forces between particles in a solid must be
broken (requires energy)
• Step 2:
▫ Intermolecular forces in the liquid must be broken
(requires energy)
• Step 3:
▫ Particles of the solid are attracted to particles of
the liquid (gives off energy)
11. Dissolving a Solid in a Liquid
• Steps 1 and 2 are endothermic (heat is absorbed)
• Step 3 is exothermic (heat is given off)
• Polarity affects solubility
12. Solvation
The process by which solvent molecules
surround and interact with solute ions or
molecules.
