Chemical Reactions
Hope Dubbs
Chemical Reactions and Equations
• Chemical reactions occur when a
substance undergoes a chemical change
• Reactions take place so there is a stable
element
• A chemical equation is a representation of
a chemical reaction in which the reactants
and products are expressed as formulas
Chemical Reactions and Equations
• We use chemical equations to summarize the
process of the reactions
• Chemical equations should be balanced in order
to show that mass is conserved during a
reaction
• The principle that during chemical reactions, the
mass of the products is always equal to the
mass of the reactants, is known as the law of
conservation of mass
Reactants and Products
• In a chemical reaction, the substances that
undergo change are called reactants
• The new substances formed as a result of
that change are called products
• The arrow in the equation means that the
reaction of the reactants yields to the
product
Synthesis Reactions
• A synthesis reaction is a reaction in which
two or more substances react to form a
single substance
• The reactants may be either elements or
compounds
• The product synthesized is always a
compound
Synthesis Reactions
• The way this looks in symbol form is
A+B
AB
• An example of this equation is
2Na + Cl2
2NaCl
• An analogy to remember this reaction is
chocolate chips + cookie dough
chocolate chip cookie dough
Decomposition Reactions
• A decomposition reaction is a reaction in
which a compound breaks down into two
or more simpler substances
• The reactant in a decomposition reaction
must be a compound
• The products may be elements or
compounds
Decomposition Reactions
• The symbol form for decomposition
reactions is AB A + B
• An example of this type of equation is
2H2O
2H2 + O2
• An analogy to remember this reaction is
Peanut Butter & Jelly
Peanut Butter +
Jelly
Single Replacement
• A single-replacement reaction is a reaction
in which one element takes the place of
another element in a compound
• Single-replacement reactions look this way
in symbol form: A + BC B + AC
Single Replacement
• An example of this type of equation is
Cu + 2AgNO3 2Ag + Cu(NO3)2
• An analogy to remember this reaction is
blue + greenpurple
green + bluepurple
Double Replacement
• A double-replacement reaction is one in
which two different compounds exchange
positive ions and form two new
compounds
• The symbol form for this reaction is
AB + CD
AD + CB
Double Replacement
• An example of this type of equation is
Pb(NO3)2 + 2KI
PbI2 + 2KNO3
• An analogy to remember this reaction is
bluegreen + redpurple
bluepurple +
redgreen