Chemical Equations & Reactions

Materials: Conserving Matter

Chemical Reaction

Process by which one or more substances are changed into one or more different substances

Indications of a Chemical Reaction

1. Evolution of heat & light

Indications of a Chemical Reaction

2. Production of a gas

Indications of a Chemical Reaction

3. Formation of a precipitate

Indications of a chemical reaction

4. Change in color. (sumac leaves change color when chlorophyll is destroyed)

Chemical Reactions

There are many ways where matter seems to disappear: The consumption of fuel by your car. The lunch you ate today. The rusting away of your car.

Do they really disappear? NO

Chemical Equation

Reactants Products

Follows the Law of Conservation of Mass

Chemical Reactions

Law of Conservation of Matter: in a chemical reaction, matter in neither created nor destroyed; the molecules are merely rearranged atoms are forever! you should be able to account for every individual

atom in a chemical reaction  

Word Equation

Represents facts- only qualitative

Example:Methane + oxygen carbon dioxide + water

Writing Chemical EquationsWriting Chemical Equations

Example:

CH4(g) + O2(g) CO2(g) + H2O(g)

(not balanced)

Symbols you will see in equations

Formula Equation

Writing Chemical EquationsWriting Chemical Equations

Inserting Coefficients-small whole # that appears in front of a formula

Multiplies number of atoms of each element indicated in chemical formula

Example:

CH4(g) + 2O2(g) CO2(g) + 2H2O(g)

Balanced Formula Equation

Writing Chemical EquationsWriting Chemical Equations

Atom Inventory

Name the number and type of atoms in

AgNO3

(NH4)2CO3

6 H2O

Atom Inventory

In order to follow the law of conservation-

there must be the same number and type of atoms on both sides of the equation.

Atom Inventory

Is this equation balanced? Take an atom inventory

Mg + O2 MgO yes no

2NaOH Na2O + H2O yes no

Mg + Cl2 MgCl2 yes no

Balancing Chemical Equations

Balance the formula equation according to the law of conservation of mass Balance the different types of atoms one at a

time Balance polyatomic ions that appear on both

sides of the equation as single units Balance H atoms and O atoms after atoms of

all other elements have been balanced

Examples

Mg + HCl MgCl2 + H2

Al2(SO4)3 + Ca(OH)2 Al(OH)3 + CaSO4

MgI2 + KNO3 KI + Mg(NO3)2