Mixtures and Solutions

Mixtures

There are two types of mixtures:• Heterogeneous – mixtures that do not

blend smoothly throughout

• Homogeneous – mixtures that do blendsmoothly throughout

Suspensions

There are two types of heterogeneousmixtures:• Suspensions• Colloids

A suspension is a mixture containing largeparticles that settle out if left undisturbed.

Muddy water is an example of a suspension.

Suspensions contain particles that areusually greater than 1000 nm in diameter.

A suspension can be separated by filtration.

Colloids

A colloid is a mixture that containsmedium-sized particles that do not settleout.

Colloids contain particles that are between1 and 1000 nm in diameter.

The most abundant substance in a colloidis the dispersion medium.

Colloids scatter light. This is called theTyndall effect.

Colloids are categorized according to thephases of their dispersed particles anddispersing medium.

There are sols, emulsions, foams, andaerosols.

Milk is a colloidal emulsion, while smoke isan aerosol.

Solutions & Solubility

A solution is a homogeneous mixture oftwo or more substances.

The particles of a solution are extremelysmall – mainly atoms and ions. You cansee through a solution – it does notscatter or block light.

A solution is a mixture that appears as asingle substance but is composed ofparticles of two or more substances thatare evenly mixed.

In a solution, particles of one substancedissolve in another.

In solutions, the solute is the substancethat is dissolved and the solvent is thesubstances that is doing the dissolving.

In a solution of salt water, salt is beingdissolved in water so salt is the soluteand water is the solvent.

A solution can be a solid solution, aliquid solution (like salt water), and agaseous solution (like air). It dependson the state of the solvent.

A solid solution is called an alloy. Brassis a solid solution made when zinc is“dissolved” in copper. Zinc is the soluteand copper is the solvent.

Some combinations of substancesreadily form solutions, others do not.

A substance that dissolves in a solventreadily is said to be soluble in thatsolvent.

A substance that does NOT dissolve ina solvent is insoluble in that solvent.

When two liquids are mixed together,they either mix completely and evenly, orthey don’t mix.

Two liquids that are soluble in each otherare miscible. (ex. water and ethanol)

Two liquids that are NOT soluble in eachother are immiscible. (ex. oil and water)

“Like dissolves like”. Oil and water do notmix because one is polar (water) and theother is nonpolar (oil).

Ionic and polar solutes will only dissolve inionic or polar solvents like water. Nonpolarsolutes will only dissolve in nonpolarsolvents.

Some examples of solutions are pop, saltwater, and sugar water.

Factors that Affect SolvationSolvation occurs only when the solute and solvent particles come in contact with each other.

There are many factors that will increase solvation.

There are three ways to increase the rate of solvation:

• Agitation (stirring)• Increasing the surface area of the solute

(crushing)• Increasing the temperature

Temperature

Increasing the temperature will increasethe solubility of most solids in a liquidsolvent.

Increasing the temperature, however,decreases the solubility of gases in liquidsolvents.

This is because increased temperaturecauses an increase in kinetic energy.

The higher kinetic energy causes moremotion in the gas molecules which breakintermolecular bonds and escape fromsolution.

Pressure

Increasing the pressure will increase thesolubility of gases in liquid solvents. Itdoes not do much for solid solutes inliquid solvents, though.