Introduction to Chemical
Reactions
What is a Chemical Reaction?
It is a chemical change in which one or
more substances are destroyed and one
or more new substances are created.
BEFORE
H2 gas
and
O2gas
AFTER
H2Oliquid
Parts of a Chemical Reaction
Reactants Products
Reactants: Substances that are destroyed by the
chemical change (bonds break).
Products: Substances created by the chemical
change (new bonds form).
The arrow () is read as “yields”.
Other symbols in chemical
reactions
•(s) = solid
•(l) = liquid
•(g) = gas
•(aq) = aqueous solution (the substance is
dissolved in H2O)
• “+” separates two or more reactants or
products
• “” yield sign separates reactants from
products
Evidence for a Chemical Reaction
1) Evolution of light or heat.
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