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1
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- Putting chemical changes into words
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2
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3
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4
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- All elements are represented by a 1 or 2 letter symbol
- For example
- C = Carbon
- Ne = Neon
- O = Oxygen
- The symbols are shown on the periodic table
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5
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- Shows the elements & number of atoms of each element in a molecule
- H2SO4
- Elements
- Hydrogen; 2 atoms
- Sulfur: 1 atom
- Oxygen: 4 atoms
- 7 atoms total
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6
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- A formula may begin with a number.
- If there is no number, then “1” is understood to be in front of the
formula.
- This number is called the coefficient.
- The coefficient represents the number of molecules of that compound or
atom needed in the reaction.
- For example:
- 2H2SO4 – 2 molecules of Sulfuric Acid
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7
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- 2H2SO4 – 2 molecules of Sulfuric Acid
- A coefficient is distributed to ALL elements in a compound
- 2 – H2 (for a total of 4 H atoms)
- 2 – S (for a total of 2 S
atoms)
- 2 – O4 (for a total of 8 O atoms)
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8
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- Each side of an equation represents a combination of chemicals.
- The combination is written as a set of chemical formulas, separated by +
symbols.
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9
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- The two sides of the equation are separated by an arrow.
- The combination of chemicals before the reaction are on the left side
of the arrow
- The right side indicates the combination of chemicals after the
reaction.
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10
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- In this reaction, sodium (Na) and oxygen (O2) react to make a
single molecule, Na2O
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11
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- The Law of Conservation of Mass states that in a chemical reaction, the
quantity or amount of each element does not change.
- This means that each side of the equation must represent the same
quantity of each element; in
other words have the same number of each kind of atom.
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12
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- In order for this equation to be balanced, there must be equal amount of
Na on the left hand side and on the right hand side. Right now, there is
1 Na atom on the left but 2 Na atoms on the right. We solve this problem
by putting a 2 in front of the Na on the left hand side, Like this:
- 2Na + O2 → Na2O
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13
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- There are 2 Na's on the left and 2 Na's on the right. But what about the
O? We now must check to see if the O's are balanced on both sides of the
equation. On the left hand side there are 2 O's and the right hand side
only has one. This is still an unbalanced equation. To fix this we must
put a 2 in front of the Na2O on the right hand side. Now our
equation reads:
- 2Na + O2 → 2Na2O
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14
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- Notice that the 2 on the right hand side is "distributed" to
both the Na2 and the O. Currently the left hand side of the
equation has 2 Na's and 2O's. The right hand side has 4 Na's total and 2
O's. Again, this is a problem, there must be an equal amount of each
chemical on both sides. To fix this let's add 2 more Na's on the left
side. The equation will now look like this:
- 4Na + O2 → 2Na2O
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15
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- http://en.wikipedia.org/wiki/Chemical_equations
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Notes
