Chemical Reactions

1
Chemical Reactions
2
SC Standards

• PS-4.6
• Distinguish between chemical changes (including
  the formation of gas or reactivity with acids)
  and physical changes (including changes in size,
  shape, color, and/ or phase).
• PS-4.7
• Summarize characteristics of balanced chemical
  equations (including conservation of mass and
  changes in energy in the form of heat-that is,
  exothermic or endothermic reactions).
• PS-4.8
• Summarize evidence (including the evolution of
  gas the formation of a precipitate and/ or
  changes in temperature, color, and/ or odor) that
  a chemical reaction has occurred.
• PS-4.9
• Apply a procedure to balance equations for a
  simple synthesis or decomposition reaction.
• PS-4.10
• Recognize simple chemical equations (including
  single replacement and double replacement) as
  being balanced or not balanced.
• PS-4.11
• Explain the effects of temperature,
  concentration, surface area, and the presence of
  a catalyst on reaction rates.

3
Signs of a Chemical Reaction

• Production of light
• Formation of a gas
• Formation of a precipitate
• Color change
• Change in temperature

4
Law of Conservation of Mass

• mass is neither created nor destroyed in a
  chemical reaction

total mass stays the same
atoms can only rearrange
4 H 2 O
4 H 2 O
36 g
4 g
32 g
5
Chemical Equations

• AB ? CD

PRODUCTS
REACTANTS
6
Chemical Equations
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Types of Chemical Reactions
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Synthesis

• the combination of 2 or more substances to form a
  compound
• only one product

A B ? AB
9
Synthesis

• H2(g) Cl2(g) ? 2 HCl(g)

10
Decomposition

• a compound breaks down into 2 or more simpler
  substances
• only one reactant

AB ? A B
11
Decomposition

• 2 H2O(l) ? 2 H2(g) O2(g)

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Single Replacement

• one element replaces another in a compound
• metal replaces metal ()
• nonmetal replaces nonmetal (-)

A BC ? AC B
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Single Replacement

• Cu(s) 2AgNO3(aq) ? Cu(NO3)2(aq) 2Ag(s)

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Double Replacement

• ions in two compounds change partners
• cation of one compound combines with anion of the
  other

AB CD ? AD CB
15
Double Replacement

• Pb(NO3)2(aq) K2CrO4(aq) ? PbCrO4(s) 2KNO3(aq)

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Double Replacement Reaction Lab