Chemical Chemical Equations Equations

& & ReactionsReactions

Chapter 8

Chemical Chemical ReactionReaction The process by which the atoms of one or more substances are rearranged to form different substances

Another name for a chemical reaction is a chemical change.

Chemical Chemical ReactionReaction

5 Evidences of a 5 Evidences of a Chemical ReactionChemical Reaction

1. Production of heat and/or light2. Color Change3. Odor4. Gas Bubbles5. Formation of a solid

(precipitate)

Chemical ReactionsChemical Reactions

Chemist use equations to represent

chemical reactions.

ReactantsReactants

Starting substances on left side of arrow what you start with

ProductsProducts

Substances formed during the reaction on right side of arrow what you end with

Chemical ReactionsChemical Reactions

During chemical reactions the reactants are used up as the products are formed – the equation shows the directions of progress

Chemical EquationsChemical Equations

Chemist use an arrow (→) in the equations instead of an equal sign like mathThe arrow stands for “yields”Or “reacts to produce”

Chemical EquationsChemical Equations

A plus sign (+) is used to separate 2 or more reactants or products

Chemical EquationsChemical Equations

1.Solid State : (s) 2.Liquid State : (l) 3.Gas State : (g) 4.Aqueous Solution : (aq)

Word EquationsWord Equations

A word equation describes a chemical

reaction in words rather than symbols

Word EquationsWord Equations

Iron (s) + chlorine (g)

iron (III) chloride (s)

Skeletal Skeletal EquationsEquations

Describes a chemical reaction with symbols

rather than words

Skeletal Skeletal EquationsEquations

Fe (s) + Cl2 (g) FeCl3

(s)

Law of Conservationof Mass

Mass can neither be created or

destroyed during a chemical reaction

Skeletal Skeletal EquationsEquations

Skeletal equations lack the number of atoms of each reactant and product that must be present in order to carry out the reaction

Chemical Chemical EquationsEquations

A statement that uses chemical formulas to

show the identities and relative amounts of the substances involved in a

chemical reaction

Chemical Chemical EquationsEquations

Chemist use a Coefficient to balance chemical equations Number written in front of

a reactant or product Always a whole number

6 Steps to Balance a Chemical Equation

1.Write the skeleton equation for the reaction H2 (g) + Cl2 (g) HCl (g)

6 Steps to Balance a Chemical Equation

2.Count the atoms of each element in the reactants 2 H atoms + 2 Cl atoms

6 Steps to Balance a Chemical Equation

3. Count the atoms of each element in the products 1 H atom + 1 Cl atom

6 Steps to Balance a Chemical Equation

4. Add coefficients to make the number of atoms of each element equal on both sides of the equation H2 + Cl2 2HCl NEVER change the subscript!!!

6 Steps to Balance a Chemical Equation

5.Reduce the coefficients to their lowest possible ratio 1:1:2 Chemical equation must be in

most reduced form possible!

6 Steps to Balance a Chemical Equation

6. Check your work!