Chapter 3 section 3 and 4Chapter 3 section 3 and 4

MixturesMixtures

A mixture is a A mixture is a physical blendphysical blend of two or of two or more substances. more substances.

Their composition varies (Air).Their composition varies (Air).There are two types of mixtures: There are two types of mixtures:

homogenous and heterogenoushomogenous and heterogenous

MixturesMixtures

Heterogenous mixturesHeterogenous mixtures

Is the type of mixture that is not uniform in Is the type of mixture that is not uniform in composition.composition.

If you were to sample one portion of such If you were to sample one portion of such a mixture, it’s composition would be a mixture, it’s composition would be different from that of another portion.different from that of another portion.

MixturesMixtures

Homogenous mixtureHomogenous mixture

Is the type of mixture that has a Is the type of mixture that has a completely uniform composition completely uniform composition

throughout itself.throughout itself.

It’s components are evenly distributed It’s components are evenly distributed throughout the sample. throughout the sample.

Homogenous or Heterogenous?Homogenous or Heterogenous?

1.1. AirAir

2.2. Salt waterSalt water

3.3. TeaTea

4.4. BrassBrass

5.5. VinegarVinegar

6.6. Hydrogen peroxideHydrogen peroxide

7.7. SteelSteel

1.1. Salad dressingSalad dressing

2.2. AppleApple

3.3. SandSand

4.4. PaintPaint

5.5. GraniteGranite

6.6. Laundry detergentLaundry detergent

7.7. CerealCereal

SolutionsSolutions

Is the special name that scientists give to Is the special name that scientists give to homogenous mixtures.homogenous mixtures.

Solutions may be gases, liquids or solids.Solutions may be gases, liquids or solids.An example: solution of sugar in water.An example: solution of sugar in water.

SolutionsSolutions

Some common types of solutionsSome common types of solutions

System Examples System Examples

Gas-gasGas-gas COCO2 2 and O in N (air) and O in N (air)

Liquid-gasLiquid-gas Water vapor in airWater vapor in air

Gas-liquidGas-liquid COCO22 in in HH22O (Soda water)O (Soda water)

Liquid-liquidLiquid-liquid Acetic acid in HAcetic acid in H22O (vinegar)O (vinegar)

Solid-liquidSolid-liquid NaCl in NaCl in HH22O (brine)O (brine)

Solid-solidSolid-solid Cu in Ag (Sterling silver)Cu in Ag (Sterling silver)

Phases in a homogenous mixturePhases in a homogenous mixture

PhasesPhases

Any Any part of a system with uniform part of a system with uniform compositioncomposition and properties is called a and properties is called a phasephase..

On a homogenous mixture you have “one On a homogenous mixture you have “one phase” only.phase” only.

On a heterogenous mixture you have “two On a heterogenous mixture you have “two or more phases”.or more phases”.

Phases in a heterogenous mixturePhases in a heterogenous mixture

SuspensionsSuspensions

A A SUSPENSION SUSPENSION is a is a heterogeneous mixture of heterogeneous mixture of large particles large particles

These particles are visible These particles are visible and will settle out on and will settle out on standing standing

Examples of suspensions Examples of suspensions are: fine sand or silt in are: fine sand or silt in water or Italian salad water or Italian salad dressing dressing

Separating MixturesSeparating Mixtures

Suppose you had a mixture of iron nails, Suppose you had a mixture of iron nails, salt and water…salt and water…

How would you separate this mixture How would you separate this mixture completely? completely?

Based on which physical properties would Based on which physical properties would you base your method on? you base your method on?

Separating MixturesSeparating Mixtures

Mixtures can be separated based on different Mixtures can be separated based on different physical properties of the componentsphysical properties of the components..

EvaporationVolatility

ChromatographyAdherence to a surface

FiltrationState of matter

(solid/liquid/gas)

DistillationBoiling point

TechniqueDifferent Physical Property

Created by G.Baker www.thesciencequeen.netCreated by G.Baker www.thesciencequeen.net

What are elements?What are elements? Elements are the alphabet to Elements are the alphabet to

the language of molecules.the language of molecules. To make molecules, you To make molecules, you

must have elements. must have elements. Elements are made of Elements are made of

atoms. While the atoms may atoms. While the atoms may have different weights and have different weights and organization, they are all organization, they are all built in the same way.built in the same way.

Created by G.Baker www.thesciencequeen.netCreated by G.Baker www.thesciencequeen.net

More about Elements..More about Elements..ElementsElements are the building are the building

blocks of all matter. They blocks of all matter. They are made of atoms.are made of atoms.

The periodic table is a list of The periodic table is a list of all of the elements that can all of the elements that can build matter. It’s a little like build matter. It’s a little like the alphabet of chemistry.the alphabet of chemistry.

CompoundsCompounds A A compoundcompound is a is a

substance whose smallest substance whose smallest unit is made up of atoms of unit is made up of atoms of more than one element more than one element bonded together.bonded together.

• Compounds often have Compounds often have properties that are different properties that are different from the elements that from the elements that make them up. make them up.

• Examples: Water, salt, Examples: Water, salt, sugarsugar

HH220 is the chemical 0 is the chemical formula for water, and formula for water, and HH22OO22 is the formula for is the formula for hydrogen peroxide.hydrogen peroxide.

The formula tells you The formula tells you which elements make which elements make up a compound as up a compound as well as how many well as how many atoms of each atoms of each element are present. element are present.

Compounds Have FormulasCompounds Have Formulas

How to read a formulaHow to read a formula

HH2200This is a subscript. It tells us how many atoms of that element exist in one unit of that compound.

Hydrogen is made of 2 H atoms and 1 O atom.

No subscript is used when only one atom of an element is present.

Let’s try it…Let’s try it… Using your white board tell how many atoms there Using your white board tell how many atoms there

are in each element.are in each element. Sulfuric AcidSulfuric Acid HH22SOSO44

2 Hydrogen2 Hydrogen4 Oxygen4 Oxygen

Hydrogen Peroxide HHydrogen Peroxide H22OO22

2 Hydrogen2 Hydrogen2 Oxygen2 Oxygen

And some more formulas…And some more formulas…Carbon Dioxide COCarbon Dioxide CO22

1 Carbon1 Carbon2 Oxygen2 Oxygen

Carbon Monoxide COCarbon Monoxide CO1 Carbon1 Carbon1 Oxygen1 Oxygen

Calcium Carbonate Calcium Carbonate (Found in shells, eggshells, antacid) (Found in shells, eggshells, antacid) CaCOCaCO33

1 Calcium1 Calcium1 Carbon1 Carbon3 Oxygen3 Oxygen

Compound ReviewCompound Review   A pure compound has the same elements A pure compound has the same elements

and the same amount of elements all of the and the same amount of elements all of the time time

Elements are chemically combined Elements are chemically combined Compound properties are different from the Compound properties are different from the

properties of the elements properties of the elements They cannot be separated physically They cannot be separated physically Physical properties such as boiling point or Physical properties such as boiling point or

melting point of pure substances are do not melting point of pure substances are do not change change

Compounds vs MixturesCompounds vs Mixtures

CompoundsCompoundsMixturesMixtures

Combine chemically forming molecules

Not chemically Not chemically combinedcombined

Combine in set proportions

Can combine in any Can combine in any proportionproportion

Separated chemically Separated Separated physicallyphysically

Law of Definite Proportions and Law of Definite Proportions and Law of Multiple ProportionsLaw of Multiple Proportions

Joseph Proust (France 1799)Joseph Proust (France 1799)

Law of Definite Law of Definite Proportions:Proportions:

A given compound A given compound always contains elements always contains elements in a certain proportion by in a certain proportion by mass. (Constant mass. (Constant composition).composition).

Atoms combine in whole number ratios, so Atoms combine in whole number ratios, so their proportion by mass will always be the their proportion by mass will always be the same.same.

Example: HExample: H22O is always made up of 2 O is always made up of 2

atoms of H and one atom of O.atoms of H and one atom of O.

The ratio of O to H in water is always 16:2 or The ratio of O to H in water is always 16:2 or 8:1.8:1.

Example:Example:

KCl always contains one atom of K for KCl always contains one atom of K for every one atom of Clevery one atom of Cl

In KCl, potassium and chlorine always In KCl, potassium and chlorine always have a ratio of “39.09 to 35.45” or “1.1 to have a ratio of “39.09 to 35.45” or “1.1 to 1” by mass. 1” by mass.

Law of Multiple ProportionsLaw of Multiple Proportions (John Dalton) (John Dalton)

When the same two elements combine to When the same two elements combine to form form more than one compound:more than one compound:

the ratios of the the ratios of the mass ofmass of one element one element in in the first compound the first compound to its mass to its mass in the in the second compound, (as it combines with second compound, (as it combines with the same mass of the other element), can the same mass of the other element), can always be expressed as ratios of small always be expressed as ratios of small whole numbers( ex: 1:3 or 2:5).whole numbers( ex: 1:3 or 2:5).

Example of Example of Law of Multiple ProportionsLaw of Multiple Proportions

Carbon combines Carbon combines with oxygen to form with oxygen to form CO and COCO and CO22 . .

Mass of Carbon(g)

Mass of Oxygen(g)

Ratio of O in CO2 to O in CO

CO 12.01 16.00

CO2 12.01 32.00 2:1

Practice Problem 1Practice Problem 1

In the carbon compounds ethane (CIn the carbon compounds ethane (C22HH66) )

and ethene (Cand ethene (C22HH44), what is the lowest ), what is the lowest

whole number ratio of H atoms that react whole number ratio of H atoms that react with the same number of C atoms? with the same number of C atoms?

Answer: 3:2 Answer: 3:2

Practice Problem 2Practice Problem 2

Carbon reacts with oxygen to form two Carbon reacts with oxygen to form two compounds as shown: compounds as shown:

Compound A: 2.41 g C, 3.22 g O. Compound A: 2.41 g C, 3.22 g O. Compound B: 6.71 g C, 17.9 g O. Compound B: 6.71 g C, 17.9 g O.

Find the lowest whole number ratio of C Find the lowest whole number ratio of C that react with an equal mass of O.that react with an equal mass of O.

Solution StrategySolution Strategy

1.1. Find the grams of carbon per 1 g of Find the grams of carbon per 1 g of oxygen for each compound.oxygen for each compound.

2.2. Divide the highest answer by the Divide the highest answer by the smallest answer.smallest answer.

Answer: 2:1Answer: 2:1

Practice Problem 3Practice Problem 3

Lead forms two compounds with oxygen as Lead forms two compounds with oxygen as shown:shown:

Compound A: 2.98 g Pb, 0.461 g O.Compound A: 2.98 g Pb, 0.461 g O. Compound B: 9.89 g Pb, 0.763 g O.Compound B: 9.89 g Pb, 0.763 g O.

For a given mass of oxygen, what is the lowest For a given mass of oxygen, what is the lowest whole number mass ratio of lead in the two whole number mass ratio of lead in the two compounds? compounds?

Answer: 2:1Answer: 2:1

Law of Conservation of Matter (Mass) The total mass of substances does not change

during a chemical reaction.

reactant 1 + reactant 2

product

total mass total mass=

calcium oxide + carbon dioxide

calcium carbonate

CaO + CO2

CaCO

3

56.08g + 44.00g

100.08g