• Make two columns on a sheet of paper. Title 1 column Physical Changes and the 2nd column title Chemical Changes.

• From the next slide, categorize each item either physical or chemical change.

PHYSICAL OR CHEMICAL Change?

Candle waxmelting

Salt dissolved in water

Fireworks exploding

Wood burning Leaves changing colors Cooking an egg

Cake bakingBreaking an egg

Cutting paper

Ice freezing Water boiling Mixing baking soda and water

Iron rusting Tarnished silver Battery corrosion

Chemistry Background• In order for elements to be completely stable

(or un-reactive) they need to have 8 electrons in their outside energy level.

• An element with 8 electrons on its last level is a happy element. The “happiest” elements on the table are the noble gases.

• Exception: Helium is happy with two electrons in its outer energy level.

Selection Process

• Sodium contains 1 valence electron on its outside shell. It is very unhappy and unstable. It needs a “partner” to balance it out. But, only one type of “partner” will do. It must have 7 valence electrons!

Match

• Chlorine looks like a good partner because it has 7 valence electrons!

• Draw a Lewis Dot Diagram for Sodium and Chlorine.

Chemistry of Sodium and Chlorine• If sodium gives away its last electron, it will be left with 8

on its last shell! Therefore it will be happy!

81e-

2

The sodium atom then becomes a ____________ion.

11P+

positive

Chemistry of Sodium and Chlorine

• If chlorine accepts the electron from sodium it will now have 8 electrons on its outside shell therefore it will be happy!

28

7e-1e-

17P+

The chlorine atom then becomes a ___________ ion.negative

Ion

an atom that has an electrical charge because it no longer has an equal number of protons and electrons.

6P+

6N2e- 3e-

Sodium Chloride

1e-

1e-

11P+1e-

7e-

17P+8e-

8e-

Rule of Eight

Molecule Possible Not Possible

LiFHHeBeONaClKICaSMgOFArKCl

Copy the table and identify if each of the following compounds is possible.Explain why!

Models of Compounds

• Make the following compounds by fitting the puzzle pieces together. Use the names of the compounds as clues.

– Sodium chloride– Calcium oxide– Carbon dioxide– Calcium chloride– Aluminum oxide

• Draw the compounds in your notebook and write the name of the compound and its chemical formula. Include the Lewis Dot Diagram for each atom

Chemical Equations

• Shorthand way that scientists use to represent what takes place in a chemical reaction.

• Chemical equations consist of many different components (parts).

Components of a Chemical Equation

2Na2O2 + 2H2O -> 4NaOH + O2

Chemical Formula Total # of Elements inthe Formula

Total # of Atoms in the Formula

NaCl

CO2

H3PO4

2H2SO4

H2O

2C6H12

Copy the chart and fill in the spaces.

Symbol

Ex: H, Na1 or 2 letters used to represent an element

Place of discovery, scientist, or other language such as Latin or Greek.

First letter capitalized, second letter lower case.

Chemical Formula

Ex: NaCl, H2O

A combination of symbols and numbers that represent the number and types of elements(atoms) present in a compound.

Subscript

Ex: CO2, H2O2

Small number written to the right and below the normal line of letters.

Shows how many atoms of each element are present in a substance.

No subscript means there is only one atom present.

Chemical Reaction

• Ex: H2 (g) + O (g) H2O (liquid)

• When substances interact to form one or more new substances with different properties than the original substance

Chemical Equation• Ex: 2H2 + 2O2 2H2O2

• A combination of chemical formulas used to describe what happens in a chemical reaction.

• The equation identifies the reactants and resulting products.

Coefficient

• 2Na + 2Cl 2NaCl

• A number written in front of a chemical formula to show how many molecules of that substance are present.

Reactants

• 2CO2 2C + 2O2

• Formulas written on left side of arrow ( )

• Starting substance or substances in a chemical reaction

Product

• 2Fe + O2 2FeO

• Formulas written on the right side of arrow ( )• New substance or substances formed in a chemical

reaction

Yields

• H2 + O2 H2O2

• Arrow shows a reaction has taken place.• The reactants have reacted to produce a

new substance (the product)

Compound

H2O, CO2, CO

A substance composed of two or more elements chemically combined

in a definite proportion

Physical Change

• A change in which the characteristics of a substance are only changed physically and the original properties stay the same.

Physical Properties

• Physical properties of matter are characteristics that you can observe about the matter.

• EX: color, shape, size, density, melting point, boiling point, freezing point, specific heat, state, metal, nonmetal, metalloid, evaporation, condensation, crystallization, conductivity, magnetism, luster, malleability, taste, dissolving, odor, texture, volume, mass, length, temperature

Chemical Changes

• A change in which a substance or substances is changed into one or more new substances with different properties than the original substances

Chemical Properties

• Chemical properties of matter are the properties that indicate whether an object can undergo a chemical reaction.

• EX. flammable, reactive, corrosive, tarnishing, rusting oxidation …

Law of Conservation of Mass

• Matter is neither created or destroyed, only changed.

• The number of atoms in the reactants must be equal to the number of atoms in the product.

Precipitate• A solid that forms as a result of a chemical

reaction

• It will pull out and fall to the bottom of the container

Law of Conservation of Mass

• Reactants yields Products

• NaHCO3 + HC2H3O2 CO2 + H2O + NaC2H3O2

• 1 sodium, 5 hydrogens, 3 carbons, 5 oxygens

• BALANCED!!!

• Number and kind of atoms on the reactant side must equal the number and kinds of atoms on the product side of the equation.

CHEMICAL CHANGES Occur When:

Different substances with new properties are formed.

Chemical Equations

• You can explain a chemical reaction on paper by using a chemical equation.

• reactants products

• What you START with What you end up with

yields

Chemical Reactions

Involve the breaking or forming of chemical bonds causing atoms to

become rearranged into a new substance or substances.

What to look for in a chemical change:

• New substance with new properties• Energy involved

(heat being released, heat being absorbed)

• Gases released• Color change• A precipitate( a solid that separates out of a

reaction)