Chemical Changes
Also called
Indicators of Chemical Reactions
1.
2.
3.
4.
Chemical Reactions
Chemical reactions are represented by sentences known as
Iron + Oxygen ------------> Iron(III) Oxide
This form is called
Fe + O2 -----------> Fe2O3
This is the above equation as a
The items on the left hand side of the arrow are called
the
The items on the right hand side are called the
The arrow is read as
1
Energy in Reactions
Energy - The ability to
The SI unit of energy is the
Kinetic Energy (KE) Potential Energy (PE) Law of Conservation of Energy - Energy can not be created
or destroyed.
calorie -
Exothermic vs. Endothermic
Exo - means
Endo - means
2
Physical States in Reactions
CH4, O2, water vapor and CO2 are all normally
CH4 (g) + 2O2 (g) -------------> CO2 (g) + 2H2O (l)
Use
6CO2 (g) + 6H2O (g) -------------> C6H12O6 (s) + 6O2(g)
Some solids will not react unless they are in
Other Symbols in Reactions
Catalyst - A substance that
Sunlight
6CO2 (g) + 6H2O (g) -------------> C6H12O6 (s) + 6O2 (g)
3
Writing Balanced Equations
For mass to remain constant, the number of
In balancing equations, you can
Coefficients - Whole Numbers you put
Little 2, Little 3 Switch
Consider the burning steel wool. Balance this equation:
Use a system of rules to balance equations.
Rule #1.
4
Rule #2
Work left to right. Repeat this process for each atom until you
can say
How many Fe atoms on the
Rule #3
Silver Nitrate plus Magnesium Chloride yields
First - Write the formula equation:
Rule #3 - Treat the polyatomic ions
5
Sample Problem A
Calcium Phosphate + Aluminum Nitrate
yields
First step: Write the formula equation from the word equation:
Rule #4
Methane
plus oxygen yields
First - Write the formula equation:
Rule #4 - In equations where elements such as oxygen (O2)
become incorporated into a compound as a single O atom -
6
Sample Problem B
Carbon Dioxide + water yields
Classifying Chemical Changes
There are many types of chemical reactions. Five broad
categories are:
1.
2.
3.
4.
5.
7
Direct Combination (Synthesis)
Two OR more reactants combine to form
General Form =
Examples:
It does not have to be single elements. It can also be two
compounds that are combining to form a new single
compound
Decomposition
Single compound is
General Form =
Example:
Dissociation – is the splitting
General Form =
Example:
8
Single Replacement
Atoms of an uncombined element
General Form =
Example:
Activity Series
In a single replacement reaction, you must
check
Example:
Mg + Li2SO4 ------------->
9
Double Replacement
Exchange of cations between two compounds
General Form =
In DR reactions one of the products
1. One product
Na2S (aq) + Cd(NO3)2 (aq) ------>
2. One product is a
2NaCN (aq) + H2SO4 (aq) ------>
3. One product is a
Ca(OH)2 (aq) + 2HCl (aq) ------>
Combustion
Also called
General Form
Example:
OR
General Form =
Example:
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