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Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
81
Chemical Reactions
Chemical Reactions
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
9
9.1 Reactions and Equations
The process by which atoms of one or more substances are
rearranged to form different substances is called a chemical
reaction. There are a number of possible indications that a chemical
reaction has occurred. Among these are absorption of heat and
release of energy in the form of light or heat, color change, production of an odor, and appearance of gas bubbles or a solid.
Statements called equations are used to represent chemical reactions. Equations indicate the reactants, or starting substances, and
the products, or substances formed during the reaction. The reactants are written to the left of an arrow that stands for “yields,” and
the products are written to the right. Plus signs are used to separate
the different reactants or products. The symbols (s), (l), (g), and (aq)
indicate solid, liquid, gas, or water solution (aqueous), respectively.
Equations can be in the form of word equations, in which the
reactants or products are indicated by their names. Word equations
can be replaced by skeleton equations, which use chemical formulas
rather than words to identify reactants and products. Skeleton equations are more informative than word equations because skeleton
equations identify the atoms that make up each reactant and product.
Example Problem 9-1
Writing Word and Skeleton Equations
Write a word equation and a skeleton equation for the reaction in
which hydrogen gas reacts with oxygen gas to form liquid water.
The word equation uses the names and physical states of the reactants and products, along with the arrow and plus symbols.
hydrogen(g) ϩ oxygen(g) 0 water(l)
The skeleton equation replaces the names of the substances with
their chemical formulas.
H 2 (g) ϩ O 2 (g) 0 H 2 O(l)
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
81
Chemical Reactions
Chemical Reactions
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
9
9.1 Reactions and Equations
The process by which atoms of one or more substances are
rearranged to form different substances is called a chemical
reaction. There are a number of possible indications that a chemical
reaction has occurred. Among these are absorption of heat and
release of energy in the form of light or heat, color change, production of an odor, and appearance of gas bubbles or a solid.
Statements called equations are used to represent chemical reactions. Equations indicate the reactants, or starting substances, and
the products, or substances formed during the reaction. The reactants are written to the left of an arrow that stands for “yields,” and
the products are written to the right. Plus signs are used to separate
the different reactants or products. The symbols (s), (l), (g), and (aq)
indicate solid, liquid, gas, or water solution (aqueous), respectively.
Equations can be in the form of word equations, in which the
reactants or products are indicated by their names. Word equations
can be replaced by skeleton equations, which use chemical formulas
rather than words to identify reactants and products. Skeleton equations are more informative than word equations because skeleton
equations identify the atoms that make up each reactant and product.
Example Problem 9-1
Writing Word and Skeleton Equations
Write a word equation and a skeleton equation for the reaction in
which hydrogen gas reacts with oxygen gas to form liquid water.
The word equation uses the names and physical states of the reactants and products, along with the arrow and plus symbols.
hydrogen(g) ϩ oxygen(g) 0 water(l)
The skeleton equation replaces the names of the substances with
their chemical formulas.
H 2 (g) ϩ O 2 (g) 0 H 2 O(l)