How can homogeneous and

heterogeneous mixtures be…

1. …classified?

2. …separated?

1. HETEROGENEOUS

MIXTURE

2. COLLOID

3. EMULSION

4. SUSPENSION

5. FILTRATION

6. TYNDALL EFFECT

7. HOMOGENEOUS

MIXTURE

8. SOLUTION

9. SOLUTE

10. SOLVENT

11. MISCIBLE LIQUID

12. DISTILLATION

Cannot be decomposed into simpler

substances by chemical change

114 known elements

2 more predicted

Two or more

elements combined

with chemical bonds

Can be decomposed into

simpler substances

Chemical changes

needed

2+ substances NOT chemically combined.

Variable composition: made of more than 1 substance

Components retain their characteristic properties

Separate using physical change

Variable composition

› English: made of a variety of substances

Components retain their characteristic

properties

› English – salt is salt, water is water

May be separated into pure substances

by physical methods – see next slide

Distill

Evaporate

Let them settle/use centrifuge

Filter

Chromatography

Same throughout - texture, color, etc.

Components indistinguishable

Separate w/physical change

Example: sweetened drinks

Smallest particle size – molecular/atomic size Solute = what is dissolving (e.g. salt) Solvent = what the solute is dissolving in, which is usually a fluid- liquid or gas (e.g. water) Solvent pulls apart the molecules of the solute. Does not usually separate on its own – because the solvent holds the particles of the solute tightly (evaporation, distillation)

Water dissolves

many

substances

Ionic or polar

covalent

Solids in solids - Alloys – e.g. brass

Gases in gases – air is a homogeneous

mixture of gases

Gases in liquids – carbon dioxide in water

(carbonated drinks)

Solutions made from

liquids

Mix totally

Example: water and

rubbing alcohol

Separate via distillation

Some liquid solutions do

not contain water, e.g.

petroleum

Homogeneous mixture

Look like solutions.

A substance trapped inside another

substance.

Particles about size of bacteria (not

visible w/out microscope)

Tyndall effect.

Separated via

distillation/evaporation

For example: shaving cream, latex

paing

Boil the liquid,

forming a vapor,

then condense

vapor into liquid

again

Heat solution, the liquid evaporates the

solid left behind.

Example: separating salt from water

1.Emulsion

2.Suspension

3.Heterogeneous

Particles broken up – smaller than mud,

larger than bacteria

Need to be centrifuged

E.g. homogenized milk, mayonnaise

Solid mixed with liquid

Settles by itself (e.g. orange juice, mud in

water)

Separated via filtration

Like a snow-globe, unhomogenized milk

Particles are size of fine mud particles

Incompatible substances (no dissolving)

Separate easily on their own (e.g. by density)

Gravitational pull only (settling).

Examples: Water and Oil, oil and salt

Centrifuge, natural settling

Assignment

Solution Heterogeneous mixture Colloid

Define Two or more substances

which do not dissolve. Repel

each other.

Example Lava lamp, oil and vinegar,

coffee (before you filter it)

How are they

separated?

Filtration

How is it similar

to…

A heterogeneous

mixture?

A colloid?

A solution?

don’t dissolve; big particles

Your assignment

1. Why is water called the universal

solvent?

2. How do substances dissolve?

3. How do solutes affect a solution?

1. Polar compound

2. Nonpolar

compound

3. Hydrogen bond

Uneven distribution of charge

› Ionic compounds – polar

› Some molecular (covalent) compounds too

Water – polar covalent compound

Water dissolves polar compounds

because water molecules attract both

positive and negative ions

Polar water molecules pull ionic crystals apart, as shown below.

• The partially negative oxygen atoms of water molecules attract the

positively charged sodium ions.

• The partially positive hydrogen atoms of water molecules attract the

negatively charged chloride ions.

Dissolving depends on the forces between particles. › The forces between the solvent molecules and the

particles of the substances must be greater than the force between the particles in the crystal.

Water dissolves many NONPOLAR compounds. › Water forms hydrogen bonds with NONPOLAR

molecular compounds such as sugar.

hydrogen bond: the intermolecular force occurring when a hydrogen atom that is bonded to a highly electronegative atom of one molecule is attracted to two unshared electrons of another molecule

Like dissolves like. › A solvent will dissolve substances that have

molecular structures that are like the solvent’s structure.

Nonpolar compounds usually will not dissolve in water. › nonpolar: describes a molecule in which the

centers of positive and negative charge are not separated

› Nonpolar solvents are used to dissolve nonpolar materials.

〉 Why do substances dissolve?

〉 The energy transferred from the solvent

to the solute, as well as the attractive

forces between the solvent and solute

molecules, causes molecules at the

surface of the crystal to dissolve.

Solutes with a larger surface area dissolve faster. › More solute particles are exposed to the solvent.

Stirring or shaking a solution helps the solute dissolve faster. › Dissolved solute particles diffuse throughout the

solution faster. › More solute particles can dissolve.

Solutes dissolve faster when the solvent is hot. › Collisions occur between solute and solvent

particles more frequently and with more energy.

Solutes affect the physical properties of a solution. › Solutes increase the boiling point of a solution.

If you dissolve salt in water, it will boil at a higher temperature.

› Solutes lower the freezing point of a solution. The coolant mixture of ethylene glycol and

water keeps a car’s radiator fluid from freezing in winter.

Polar-polar

› Water-salt

› Ethanol-ink

Nonpolar-nonpolar

› Oil paint + nonpolar solvent

Surface area

Stirring/shaking

Heat

Solutes affect the physical properties of a solution. › Solutes increase the boiling point of a solution.

If you dissolve salt in water, it will boil at a higher temperature.

› Solutes lower the freezing point of a solution. The coolant mixture of ethylene glycol and

water keeps a car’s radiator fluid from freezing in winter.

1. What is solubility?

2. How do saturated solutions react when

more solute is added?

3. What is concentration, and how can it

be calculated?

Solubility

Concentration

Saturated solution

Unsaturated solution

Supersaturated solution

Molarity

〉 What is solubility?

〉 The solubility of a substance is the maximum mass of a solute that can dissolve in 100 g of solvent at a certain temperature and standard atmospheric pressure.

solubility: the ability of one substance to dissolve in another at a given temperature and pressure

Different

substances have

different

solubilities.

How much of substance is in a solution?

To express how much of a substance can dissolve in a solvent, you need to use the concentration.

Concentration: the amount of a particular substance in a given volume of a mixture, solution, or ore › A concentrated solution has a large amount of

solute.

› A dilute solution has only a small amount of solute.

〉 What happens when you add more solute to a saturated solution?

〉 In a saturated solution, the dissolved solute is in equilibrium with undissolved solute. So, if you add more solute, it just settles to the bottom of the container.

saturated solution: a solution that cannot dissolve any more solute under the given conditions

Unsaturated solutions can become saturated.

unsaturated solution: a solution that contains less solute than a saturated solution does and that is able to dissolve additional solute

Heating a saturated solution can dissolve more solid. › The solubility of most solutes increases with

temperature.

supersaturated solution: a solution that holds more dissolved solute than is required to reach equilibrium at a given temperature. › To make a supersaturated solution, you

raise the temperature of a solution, dissolve more solute, then let the solution cool again.

Temperature and pressure affect the solubility of gases.

Gaseous solutes are less soluble in warmer water. • Example: Soda goes flat quickly at room temperature.

Gases are more soluble under higher pressure. • Example: When a can of soda is opened, carbon dioxide gas

that had been dissolved in the soda bubbles out of solution.

〉 How do you describe how much of a solute is in a solution?

One of the most common ways of expressing the concentration of solution is molarity.

Molarity: a concentration unit of a solution expressed in

moles of solute dissolved per liter of solution.

mol

= , or M L

moles of solutemolarity

liters of solution

Concentration = mass ÷ molar mass ÷

volume

M = Grams ÷ g/mol ÷ Liters

OR M = mol ÷ liters

Example:

What is the concentration of a solution

which contains 36 moles of magnesium

carbonate in 0.1 liters?

36 moles ÷ 0.1 liters = 360 M

Moles = Concentration x volume

mol = M x L

Example:

How many moles of hydrochloric acid are

in 0.300 liters of a 2 M solution?

Moles = 2M x 0.300 liters = 0.6 moles

Mass = Concentration x volume x molar

mass

g = M x L x g/mol

Example:

How many grams of

Copper (II) sulfate· 5H2O are required to

make 0.200 L of a 1M solution? The molar

mass of Copper (II) sulfate · 5H2O is

249.72 g/mol.

1. Calculating Molarity 1. M = mol ÷ L

2. M = g ÷ g/mol ÷ L

2. Calculating Volume 1. L = M x mol

2. L = g x g/mol

3. Calculating Moles 1. mol = M x L

4. Calculating Mass 1. g = M x L x g/mol