Parts of Equations Notes.notebook
November 05, 2012
Chemical
Reactions &
Equations
Chemical
Reaction
Chemical
Change
Parts of Equations
Chemical Reaction
Physical Change
Oct 27­5:01 PM
Physical vs. Chemical Changes
There is a difference!!!
Physical Changes:
• Changes in one or more physical properties of a
substance WITHOUT changing the chemical make-up.
• What are examples of physical properties???
texture
shape
size
color
volume
mass
density
physical state (solid, liquid, gas)
Oct 27­5:02 PM
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Parts of Equations Notes.notebook
November 05, 2012
Chemical Changes:
• Changes in the chemical composition of a
substance.
• AKA... CHEMICAL REACTIONS
• What are indications that a chemical change has occurred???
change in color -without external intervention
autumn leaves changing color is a chemical change
painting your house a different color is a physical change
change in energy - absorbing or releasing
can be in the form of light (fireworks)
or heat (baking a cake in the oven)
Oct 27­5:02 PM
Indications of a chemical change continued...
change in odor
not easily reversible
production of solid
production of gas
DEMOS!!!
Oct 27­5:03 PM
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Parts of Equations Notes.notebook
November 05, 2012
Equations for Demos...
Physical Changes...
vs.
ripped paper
Chemical Changes...
burned paper
paper(s) --> paper(s)
paper(s) --> smoke + ash + CO 2(g)
boiling water
hydrogen balloon
H2O(l) --> H2O(g)
2 H2(g) + O2(g) --> 2 H2O(g)
dissolving sugar
sugar decomposition
C12 H22 O11(s) --> C12 H22 O11(aq)
C12 H22 O11(s) --> 12 C(s) + 11 H 2O(g)
precipitate formation
3 CoCl2(aq) + 2 Na3PO4(aq) --> Co3(PO4)2(s) + 6 NaCl(aq)
Oct 27­5:03 PM
Parts of Equations
Consider the following equation...
reactants
"yields"
products
4 FeS2(s) + 11 O2(g) --> 2 Fe 2O3(s) + 8 SO2(g)
subscripts
coefficient
Oct 27­5:03 PM
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Parts of Equations Notes.notebook
November 05, 2012
Parts of Equations Cont...
4 FeS2(s) + 11 O2(g) --> 2 Fe 2O3(s) + 8 SO2(g)
Coefficients: represent the number of elements,
molecules or compounds in the equation
Number Subscripts: represent the number of each type
of atom in a molecule or compound
Letter Subscripts: represent the physical state of the
substance...
(s) - solid
(l) - liquid
(g) - gas
(aq) - aqueous (a substance
dissolved in water)
Example: 2 Fe2 O3(s)
2 formula units of solid iron (III) oxide
each formula unit is made of 2 iron atoms and 3 oxygen atoms
Oct 27­5:49 PM
Elements, Molecules, Compounds...
Oh my!!!
Elements:
substances made of one "type" of atom
Molecules:
substances made of more than one atom, same
or different "type", covalently bonded
Compounds:
substances made of more than one "type" of
atom
Oct 27­5:58 PM
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Parts of Equations Notes.notebook
November 05, 2012
So in the example equation...
4 FeS2(s) + 11 O2(g) --> 2 Fe 2O3(s) + 8 SO2(g)
Which is which???
element:
O2
molecules: O2, SO2
compounds: FeS2, Fe2O3, SO2
Oct 27­5:59 PM
Counting...
4 FeS2(s) + 11 O2(g) --> 2 Fe 2O3(s) + 8 SO2(g)
How many atoms of iron are in the reactants?
How many total compounds are in the equation?
How many oxygen atoms are on either side of the equation?
How many total compounds/molecules are on either
side of the equation?
Oct 27­5:59 PM
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Parts of Equations Notes.notebook
November 05, 2012
The Law of Conservation of Matter
What do you notice about the number of oxygen atoms
on either side of the equation from the previous slide?
What do you notice about the total number of compounds/
molecules on either side of the equation from the previous slide?
The Law of Conservation of Matter says...
"Matter is neither created nor destroyed
during a chemical reaction."
• The number of each type of atom is conserved
in a reaction, NOT the number of
molecules/compounds.
Oct 27­6:28 PM
Drawing Molecular Pictures
Draw a molecular picture of the following equation.
2 H2(g) + O2(g) --> 2 H 2O(g)
Oct 27­6:28 PM
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