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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