chemical reactions

–Chemical reactions occur when bonds between the outermost parts of atoms are formed or broken

–Chemical reactions involve changes in matter, the making of new materials with new properties, and energy changes.

–Symbols represent elements, formulas describe compounds, chemical equations describe a chemical reaction

Items to the LEFT of the arrow in a chemical equation are called

REACTANTS.

Na + Cl NaCl

Items to the right of the

arrow are called

PRODUCTS.

Ex: Na + Cl NaCl

Important NOTE:

No matter how many reactants and products are involved, all atoms present at the start of a reaction are present at the end.

THE TOTAL MASS OF THE REACTANTS MUST EQUAL THE TOTAL MASS OF PRODUCTS.

MATTER IS NEVER CREATED OR DESTROYED.

A number that tells how many molecules of a substance are involved in a

chemical reaction.

A coefficient of 1 is not written.

Subscripts• A subscript indicates how many

atoms of an element are in a compound

Ex. H2SO4

H= 2 S = 1 O = 4

Subscripts vs. Subscripts vs. CoefficientsCoefficients

+ -- used to separate two reactants or products.

(yields) Separates reactants and products.

Reactions that release heat.

Reactions that absorb heat.

A substance that speeds up chemical reactions.

A substance that slows down a chemical reaction.

Reactions that have hydrocarbons (CH4) and oxygen as reactants, and carbon dioxide and water as products.

Example:

C3H8 + 5O2 3CO2 + 4H2O

2Na + Cl2 2NaCl

Na2O + CO2 Na2CO3

Starts with one reactant and ends with 2 or more products.

2 KClO3 2KCl+3O2

2NaCl 2Na + Cl2

One compound and a free element that recombine to yield a new compound and new free element.

Fe + CuSO4 Cu + FeSO4

2Na + 2HCl H2 + 2NaCl

Starts with 2 compounds as reactants. These recombine to form 2 new compounds as products.

+ +

NaCl + AgNO3 NaNO3 + AgCl

KOH + HNO3 HOH + KNO3

C:\Documents and Settings\mswilliams\Local Settings\Temporary Internet Files\OLK1B5\types.htm

The first slide shows the unbalanced equation, followed

by the balanced equation.

C + O2 ----- CO2

Unbalanced

C + O2 ----- CO2

Balanced

NaCl ---- Na + Cl2

Unbalanced

2NaCl ---- 2Na + Cl2

Balanced

FeCl2 + K2S -- FeS + KCl

Unbalanced

FeCl2 + K2S -- FeS + 2KCl

Balanced

C2H4 + O2 CO2 + H2O

Unbalanced

C2H4 + 3O2 2CO2 + 2H2O

Balanced

AlCl3 + Na2CO3 Al2(CO3)3 + NaCl

Unbalanced

2AlCl3 + 3Na2CO3 Al2(CO3)3 + 6NaCl

Balanced

CS2 + O2 CO2 + SO2

Unbalanced

CS2 + 3O2 CO2 + 2SO2

Balanced

Fe + H2O Fe3O4 + H2

Unbalanced

3Fe + 4H2O Fe3O4 + 4H2

Balanced

AlCl3 Al + Cl2

Unbalanced

2AlCl3 2Al + 3Cl2

Balanced

Na + H2SO4 ---> Na2SO4 + H2

Unbalanced

2Na + H2SO4 ---> Na2SO4 + H2

Balanced

Cr + O2 CrO3

Unbalanced

2Cr + 3O2 2CrO3

Balanced