Chemical Reaction Notes
 Known amounts of elements, polyatomic ions, and/or compounds can break apart , rearrange, and form ionic or covalent bonds in new compounds in order to increase stability and decrease the total amount of chemical potential energy .

Chemical Reaction Notes
 These changes are called chemical reactions , and are different from the nuclear reactions we studied, which are when nuclei come together (or split apart) and create new atoms.

Chemical Reaction Notes
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Chemical Reaction Notes
 Chemical equations consist of a list of formulas for all of the reactants (compounds or elements added together to begin a chemical reaction) on the left side and a list of all of the products (compounds or elements which form during a chemical reaction) on the right side.

Chemical Reaction Notes
 Reactants and products are separated by an arrow.
 Reactants are separated from one another by plus signs (as are products).

Chemical Reaction Notes
 Each formula may be followed by a subscript
(solid, liquid, gas, aqueous) to show what state of matter each compound is in.
 We may represent energy
(heat, light, energy) as either a product or a reactant by writing it on the appropriate side of the equation.

Chemical Reaction Notes
 Law of Conservation of Mass: In a chemical reaction the arrangement of atoms will change , but the total number of each type of atom, and therefore the total mass , will remain constant.
http://nanopedia.case.edu/NWPage.php?page=chemical.reactions

Chemical Reaction Notes
 All chemical reactions must obey this law and therefore all chemical equations must obey it also.

Chemical Reaction Notes
 In order to ensure that our chemical equations obey the law of cons. of mass, we balance all of our equations.
 To do this:
 1. You must make sure that all of the individual compound’s formulas are correct.
 (Hydrogen, oxygen, nitrogen, and the halogens are all diatomic elements , meaning that whenever they are not found in a compound they form a molecule with themselves and have a formula with a subscript 2 ). Remember
BrINCl HOF !

Chemical Reaction Notes
 2. Pick any number and place it as a coefficient in front of any compound.
 3. You should then balance one element at a time from one side of the equation to the other by placing coefficients in front of the remaining formulas.

Chemical Reaction Notes
 4. Multiply coefficients to get rid of fractions if necessary.
 5. Reduce coefficients if necessary.

Chemical Reaction Notes
Special hints:
 1. Never change your subscripts .
 2. Balance elements that only appear in one formula on each side first .
 3. After your first “free choice” of a coefficient, you must only use coefficients that balance the element.
 Count polyatomic ions as one unit.
 Balance the element oxygen last.
 Table Team Practice.

Chemical Reaction Notes

Chemical Reaction Notes

Chemical Reaction Notes

Chemical Reaction Notes

Chemical Reaction Notes
Which of the following is NOT a chemical reaction?
A.
a piece of wood burning
B.
a car rusting
C.
an ice cube melting into water
D.
red litmus paper turning blue

Chemical Reaction Notes
What is the coefficient of bromine in the equation 2Al(s) + 3Br
2
(l) → 2AlBr
3
(s)?
A.
1
B.
2
C.
3
D.
6