WHAT WAYS CAN YOU DESCRIBE A CHEMICAL REACTION?

YOU CAN DESCRIBE A CHEMICAL REACTION BY A CHEMICAL EQUATION.

EXAMPLE: THE COMBINATION OF CH4 (METHANE GAS) AND OXYGEN PROCUCES C02 (CARBON DIOXIDE) AND H2O (WATER)

CH4 + O2 = CO2 + H20 CH4 + O2 CO2 + H2OTHE ABOVE EXAMPLES ARE UNBALNCED

A CHEMICAL REACTION IS THE PROCESS THAT CAUSES CHEMICAL CHANGES TO OCCUR. ATOMS ARE REARRANGED,CHEMICAL BONDS ARE BROKEN AND FORMED. THEREFORE, A NEW SUBSTANCE IS PRODUCED.

IN A CHEMICAL REACTION, A NEW SUBSTANCE IS FORMED, SO WHERE DO THE OLD ELEMENTS GO?

THE ATOMS OF THE ELEMENTS ARE STILL PRESENT. THEY ARE JUST REARRANGED AS THE PRODUCT. EVEN THOUGH THE ORIGINAL SUBSTANCE IS NOT PRESENT, IT APPEARS IN THE PRODUCT (NEW SUBSTANCE). BOTH THE REACTANTS AND PRODUCTS HAVE EQUAL MASSES. THIS FACT SUMS UP THE LAW OF CONSERVATION OF MATTER.

CH4 + O2 = CO2 + H20 CH4 + O2 CO2 + H2O

ATOMS IN THE REACTANTS ARE ON THE LEFT SIDE OF THE ARROW.

ATOMS IN THE PRODUCT ARE SHOWN ON THE RIGHT SIDE OF THE EQUATION

ARROWS SHOW THE DIRECTION IN WHICH THE REACTION IS GOING.

LAW OF CONSERVATION OF MASS: IN A CHEMICAL REACTION ATOMS ARE NEITHER CREATED NOR DESTROYED. ALL ATOMS PRESENT IN THE REACTANTS ARE ALSO PRESENT IN THE PRODUCT S

CHEMICAL EQUATIONS REPRESENT HOW ATOMS ARE REARRANGED IN A CHEMICAL REACTION.

BECAUSE ATOMS ARE REARRANGED AND NOT CREATED OR DESTROYED, THE NUMBER OF ATOMS OF EACH DIFFERENT ELEMENT MUST BE THE SAME ON BOTH SIDES OF THE EQUATION.

• IDENTIFY THE REACTANTS AND THE PRODUCTS IN THE FOLLOWING EQUATIONS:

CH4 + O2 CO2 + H2O

C + O2 CO2

• IMPORTANT FACTS ABOUT CHEMICAL FORMULAS IN A CHEMICAL EQUATION

THE NUMBER BELOW A CHEMICAL FORMULA IS CALLED A SUBSCRIPT

THE SUBSCRIPT REPRESENTS THE NUMBER OF ATOMS OF AN ELEMENT WITHIN A MOLECULE.

IF NO SUBSCRIPT IS THERE, A ONE IS UNDERSTOOD TO BE THERE.

• IDENTIFY THE SUBSCRIPTS IN THE FOLLOWING CHEMICAL FORMULA”

CH4 + O2

C + O2

• COEEFIECIENTS ARE NUMBERS IN FRONT OF THE CHEMICAL FORMULA AND INDICATES THE NUMBER OF PARTICLES THAT PARTICIPATE IN THE REACTION.

• IDENTIFY THE COEFFIECIENT IN THE FOLLOWING EQUATION.

CH4 + 202 CO2 + 2H20

THIS IS HOW TO DETERMINE IF AN EQUATION IS BALANCED.

• TWO NUMBERS ARE TO BE CONSIDERED. THE SUBSCRIPT & THE COEFFICIENT.

• MULTIPLY THE COEFFIENT BY THE SUBSCRIPT.

• REMEMBER, IF NO SUBSCRIPT IS WRITTEN, THE SUBSCRIPT IS UNDERSTOOD TO BE THE NUMBER ONE.

DETERMINING BALANCED CHEMICAL EQUATIONS, CONTINUED

• HOW MANY OF EACH ATOMS OF A MOLECULE ARE IN THE FOLLOWING FORMULA: 2H20

• REMEMBER, THE NUMBER OF EACH KIND OF ATOM ON THE LEFT SIDE OF THE ARROW MUST EQUAL THE NUMBER OF EACH KIND OF ATOM ON THE RIGHT SIDE OF THE ARROW FOR THE EQUATION TO BE BALANCED.

• LET’S APPLY WHAT WE’VE LEARNED TO SEE IF THE FOLLOWING EQUATION BALANCED?

2H2O 2H2 + O2

2H2O 2H2 + O2

GUIDING QUESTIONS• HOW MANY HYDROGEN ATOMS ON THE REACTANT

SIDE?

• HOW MANY HYDROGEN ATOMS ON THE PRODUCT SIDE?

• HOW MANY OXYGEN ATOMS ON THE REACTANT SIDE?

• HOW MANY OXYGEN ATOMS ON THE PRODUCT SIDE?

• SO IS THE EQUATION BALANCED? EXPLAIN. WHY OR WHY NOT.

• DOES THIS EQUATION SUPPORT THE LAW OF CONSERVATION OF MATTER? EXPLAIN WHY OR WHY NOT.

• BY YOURSELF, DETERMINE IF THE FOLLOWING EQUATION IS BALANCED.

CH4 + O2 + O2 CO2 + H2O + H20

• IS IT BALANCED OR NOT? EXPLAIN WHY OR WHY NOT.

1. MODEL THE FOLLOWING EQUATIONS USING MANIPULATIVES .

* 2H2O 2H2 + O2 * CH4 + 2O2 CO2 + 2H2O * 2Hg + O2 2HgO

2. ILLUSTRATE THE BALANCED EQUATIONS IN A DIAGRAM. REFER TO THE BALANCED EQUATION AT THE BOTTOM OF PG 581.