A solution is a homogenous mixture of 2 or more substances.

The solute is(are) the substance(s) present in the smaller amount(s).

The solvent is the substance present in the larger amount.

An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity.

A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity.

nonelectrolyte weak electrolyte strong electrolyte

A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.

An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature.

A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature.

Sodium acetate crystals rapidly form when a seed crystal isadded to a supersaturated solution of sodium acetate.

Concentration UnitsThe concentration of a solution is the amount of solute present in a given quantity of solvent or solution.

Molarity (M)

M =moles of solute

liters of solution

Three types of interactions in the solution process:• solute-solute interaction (separating the solute)• solvent-solvent interaction (overcoming intermolecular forces)• solvent-solute interaction

•Steps 1 and 2 require energy, since forces must be overcome to expand the solute and solvent.•Step 3 usually releases energy.•Steps 1 and 2 are endothermic and step 3 is often exothermic.•Enthalpy change: enthalpy (heat) of solution (∆Hsoln) is the sum of the ∆H values for the steps:

∆Hsoln = ∆H1 + ∆H2 + ∆H3

(a) ΔHsoln has a negative sign (exothermic) if step 3 releases more energy than that required by 1 and 2(b) ΔHsoln has a positive sign (endothermic) if steps 1 and 2 require more energy than is released in 3

“like dissolves like”

Two substances with similar intermolecular forces are likely to be soluble in each other.

• non-polar molecules are soluble in non-polar solvents

CCl4 in C6H6

• polar molecules are soluble in polar solvents

C2H5OH in H2O

• ionic compounds are more soluble in polar solvents

NaCl in H2O or NH3 (l)

What factors affect solubility?

Temperature and SolubilitySolid solubility and temperature – the solubility of most solids increases with temperature.

solubility increases with increasing temperature

solubility decreases with increasing temperature due to entropy (not covered yet)

Temperature and Solubility

Gas solubility and temperature

solubility usually decreases with increasing temperature (more energy to escape from solvent)

A suspension of tiny particles in some medium is called a colloidal dispersion, or a colloid.

 Dispersion Medium  Dispersed Phase  Type of colloid  Example

 Gas  Liquid  Aerosol  Fog, mist

 Gas  Solid  Aerosol  Smoke

 Liquid  Gas  Foam  Whipped cream

 Liquid  Liquid  Emulsion  Mayonnaise, hair cream

 Liquid  Solid  Sol  Paints, cell fluids

 Solid  Gas  Foam  Pumice, plastic foams

 Solid  Liquid  Gel  Jelly, cheese

 Solid  Solid  Solid Sol  Ruby glass (glass with dispersed metal)

The Tyndall effect is used to distinguish between a suspension and a true solution. Light is scattered by the suspended particles in a colloid.