Chemical Reactions

Chemical Reaction…

Not a Chemical Reaction…

What is a Chemical Reaction?

• A process in which new substances with new chemical and/or physical properties are formed.

• A burning piece of paper (Chemical Reaction): paper ashes, water vapor, and carbon dioxide

• Dissolving salt in water (No Reaction):

Salt + Water → Salt + Water

Parts of a Chemical Equation

ReactantsThe substances that

you start with. In this case:

Sodium and Chlorine

“Yields”This arrow tells

you that the reactants

become the products through a chemical reaction.

ProductsThe substances you end with.

In this case:Sodium Chloride

sodium and chlorine yields sodium chlorideNa+ Cl → NaCl

Chemical Equations

Mg + O2 → MgO

H2O → H2 + O2

C4H10 + O2→CO2 + H2O

magnesium and

andand

and

oxygen yields

yields

yields

magnesium oxide

water hydrogen oxygen

butane oxygen carbon dioxide water

Types of Chemical ReactionsType 1: Synthesis

• In a synthesis reaction, two (or more) simple substances form a more complex substance.

• Synthesis: Two Become One• A + B → AB

Synthesis Example

Na + Cl → NaCl sodium and chlorine yields sodium chloride

Types of Chemical ReactionsType 2: Decomposition

• In a decomposition reaction, a complex substance is broken down into two (or more) simpler substances.

• Decomposition: One Becomes Two• AB → A + B

Decomposition Example

H2O2 → H2O + O2hydrogen peroxide yields water and oxygen

Types of Chemical ReactionsType 3: Single Replacement Reaction

• In a single replacement reaction, a single element replaces another element in a compound.

• Single Replacement: Start with one compound, end with a different compound.

A + BC B + ACSingle Replacement Reaction

Single Replacement Example

Zn + HCl → H2 + ZnCl2 zinc and hydrochloric acid yields hydrogen and zinc chloride

Types of Chemical ReactionsType 4: Double Replacement Reaction

• In a double replacement reaction, elements from two compounds switch places and form two new compounds.

• Double Replacement: Start with two compounds, end with two different compounds.

AB + CD CB + AD

Double Replacement Reaction