Chapter 6
6.1-6.5
Chemical Changes and Reactions
Chemical and Physical Properties
Chemical Properties - chemical changes
„
„
rusting or oxidation
chemical reactions
Physical Properties - physical changes
„
„
changes of state
density, color, solubility, melting, boiling
Extensive Properties - depend on quantity
Intensive Properties - do not depend on quantity
States of Matter
Change States –
Physical Change
heating
„ cooling
„
Physical Change vs. Chemical
Change
Physical Change vs. Chemical
Change
Chemical Equations
Symbolic representation of a chemical
reaction (chemical change) that shows:
1. reactants on left side of reaction
2. products on right side of equation
3. relative amounts of each using coefficients
Chemical Equations
Attempt to show on paper what is
happening at the laboratory and molecular
levels.
Chemical Equations
Look at the information an equation
provides:
∆
Fe2O3 (s) + 3 CO(g)⎯
⎯→ 2 Fe(s) + 3 CO2 ( g)
reactants
1 formula unit
yields
3 molecules
products
2 atoms 3 molecules
States of matter also listed
Chemical Equations
Chemical Equations
Law of Conservation of Matter
There is no detectable change in quantity of matter in
an ordinary chemical reaction.
„ Balanced chemical equations must always include the
same number of each kind of atom on both sides of the
equation.
∆
3 8
2
2
2
„
C H +5O ⎯
⎯→ 3 CO + 4 H O
Balancing equations is a skill acquired only
with lots of practice
„
work many problems
Balancing Equations
Combination Reactions
Combination reactions occur when two or
more substances combine to form a
compound.
There are three basic types of combination
reactions.
1.
2.
3.
Two elements react to form a new compound
An element and a compound react to form
one new compound
Two compounds react to form one compound
Combination Reactions
? Na (s ) + ? Cl 2 (g ) → ? NaCl (s )
? Mg (s ) + ? O 2 (g ) → ? MgO(s )
? Al (s ) + ? Br2 (z) → ? AlBr3(s )
Combination Reactions
?P4 (s ) + ? O 2 (g ) → ?P4O10 (s )
_CO (g ) + _ O 2 (g ) → _ CO 2 (g )
_P4 (s ) + _ Cl 2 (g ) → _ PCl 3(z)
_SO 2 (g ) + _ O 2 (g ) ⎯
⎯→ _ SO3(g )
_P4O6 + _ O2 → _ P4O10
Decomposition Reactions
Decomposition reactions occur when one
compound decomposes to form:
1.
2.
3.
Two elements
One or more elements and one or more
compounds
Two or more compounds
Decomposition Reactions
∆
_ N 2O (g ) ⎯
⎯→ _ N 2 (g ) + _ O 2 (g )
hν
_ AgBr(s ) ⎯⎯→ _ Ag (s ) + _ Br2 (z)
Decomposition Reactions
_H2O2(aq ) ⎯
⎯→ _ H2O(z) + _ O2(g )
∆
NH 4 HCO 3(s ) ⎯
⎯→ NH 3(g ) + H 2O (g ) + CO 2 (g )
Displacement Reactions
Displacement reactions occur when one
element displaces another element from a
compound. (there are many types)
_AgNO 3(aq ) + _Cu (s) → _CuNO 3(aq ) + _ Ag (s)
_Al(s) + _H2SO4(aq ) → _Al2 (SO4 )3(aq ) + _ H2(g )
_Cl2 (g ) + _ NaI (aq ) → _I 2 (s ) + _NaCl(aq)
Displacement Reactions
_ CaCl2(aq) + _Na3PO4( aq) → _ NaCl( aq) + _ Ca3 (PO4 )2(s)
_Ca(OH)2(aq) + _HNO3(aq) → _ Ca(NO3 )2( aq) + _H2O( z)
_Ca(NO3 )2(aq) + _K2CO3( aq) → _KNO3( aq ) + _ CaCO3(s)
Reactions Overview