a combination of two or more substances that are not chemically combined and can be separated by...

A combination of two or moresubstances that are not chemicallycombined and can be separatedby physical means.

A solution is a homogeneous mixture of two or more substances in a single phase.

Thoroughly mixed

Same Composition Throughout

Same PropertiesThroughout

What makes up a solution?• Solute: the substance being dissolved

• Solvent: the substance doing the dissolving

Name the solute and solvent:

water

water

salt

Sugar, carbon dioxide

solution solute(s) solvent

Ocean water

Coca-cola

Humid air 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

LiquidWater 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?

•Electrolytes: specific aqueous solutions in which the solute dissolves to form ions.

•Aqueous solutions (aq): solutions in which water is the solvent.

•Alloys: solid solution of two or more metals.

•Amalgams: specific alloys in which one of the metals is mercury.

•Tinctures: solutions in which alcohol is the solvent.

If the particles in a solvent are so large thatthey settle out unlessthe mixture is constantlystirred or agitated, the mixture is called a suspension.

Muddy Water

Particles that are intermediate insize between those in solutionsand suspensions form mixturesknown as colloidal dispersions, or colloids.

paints, mud, gelatin, milk, mayonnaise, shaving cream, smoke, fog, butter

•A beam of light distinguishes a colloidfrom a solution.•The particles in a colloid will scatter light,making the beam visible.

NaCl Solution

Gelatin andWater

Dissolves in water to givea solution that conductsan electric current.

Ionic Compounds (NaCl)Highly Polar MolecularCompounds (HCl)

Dissolves in water to givea solution that does notconduct electrical current.

Neutral solute molecules (notcharged particles).

Sugar is a nonelectrolyte.

What does solublemean?

Is sugar more soluble in hot tea or iced tea?

By experience you knowthat sugar will dissolve intea.

Sugar is described as being “soluble” in tea.

Soluble – capable of dissolving in a particularsolvent.

Back to tea. Why does sugar dissolve faster in hottea versus iced tea?

Temperature•Heating a solventallows solvent molecules to movefaster and their kineticenergy increases.

•At higher temperatures, collisions betweensolvent molecules and the solute are morefrequent and are of higher energy.•Helps to separate solute particles from each other and have better dispersion among the solvent molecules.

•Dissolution can be spedup if surface area of solute isincreased.•Crushing sugar cubes increases its surface area.•The more finely divided a substance is, the greaterthe surface area and more quickly it dissolves.

•Stirring or shaking helps todisperse the solute particlesand bring fresh solvent intocontact with the solute surface.

•Contact between the soluteand solvent is increased.

Is there a limit to the amount of salt that will dissolve in a glass of water?

Suppose you spoon copper sulfate into water until no more will dissolve.

There is a little copper sulfate in the bottom.

This means that copper sulfate is dissolving into the water as fast as copper sulfate is crystallizing out onto the bottom.

That is dynamic equilibrium.

Solution equilibrium is the physicalstate in which the opposing processes of dissolution and crystallization of a solute occur atequal rates.

A solution that contains the maximum amount of dissolved solute is described as a saturated solution.

A solution that contains less solute than a saturatedsolution under the existing conditions is an unsaturated solution.

A supersaturated solution is a solution thatcontains more dissolved solute than a saturatedsolution contains under the same conditions.

How does a supersaturated solution form?

Heatsaturatedsolution

Let coolslowly – unstable

If disturbed –will rapidlycrystallize

The solubility of a substance is the amount of that substance requiredto form a saturated solution with a specific amount of solvent at a specified temperature.

Why does vinegar dissolve in water butnot in vegetable oil?

Type of bonding, polarity or nonpolarity of molecules,and the intermolecular forces between the solute andthe solvent.

Ionic Compounds Polar Solvents

Nonpolar Compounds Nonpolar Solvents

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.

The concentration of a solution is a measureof the amount of solute in a given amount ofsolvent or solution.

Concentration Units

Molarity is the number ofmoles of solute in one liter of solution.

The symbol for molarity is M.

For example, a “one molar” solution of sodium hydroxide, NaOH,contains one mole of NaOH in every liter of solution. The concentration of this solution would be written as 1 M NaOH.

(L)solution of volume(mol) solute ofamount

(M)molarity

Note that a 1 M solution is not made by adding 1 mol of solute to 1 L of solvent.

Molality is the concentrationof a solution expressed inmoles of solute per kilogramof solvent.

The symbol for molality is m.

For example, a “one molal” solution of sodium hydroxide, NaOH,contains one mole of NaOH dissolved in exactly 1 kg of solvent.

The concentration of this solution would be written 1 m NaOH.

(kg)solvent of masssolute moles

molality