Chemical Reactions Review!

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Chemical Reactions Review!
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What is a Chemical Reaction?

• When a chemical reaction occurs, bonds between
  atoms are formed or broken.
• This causes substances to combine and recombine
  as different molecules.
• This happens a lot inside an organisms cells!
• All the chemical reactions that occur within an
  organism are referred to as that organisms
  METABOLISM!

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What is a Chemical Reaction?

• Scientists use chemical equations to represent
  the chemical reactions. (Kind of like in math!)

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How are Chemical Reactions Classified?

• There are millions of reactions that occur every
  day. Many of them are similar and so we classify
  them into categories.
• Not every reaction can be classified under one of
  these headings because some reactions fit into
  more than one category.

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1. COMBUSTION

• Oxygen combines with other elements in
  combustion.
• These reactions are highly exothermic, releasing
  a large amount of energy as heat, light, or
  sound.
• EX CH4(g) 2O2(g) CO2(g) 2H2O (g)
  803 kJ

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2. OXIDATION

• Oxygen also participates in oxidation reactions.
• The rusting of iron is an example of an oxidation
  reaction.
• EX
• 4Fe(s) 3O2(g) 6H2O(g) 2(Fe2O3
  3H2O)(s)

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3. SYNTHESIS

• Compounds are made in synthesis reactions.
• Plants synthesize complex molecules, like starch,
  caffeine, and chlorophyll from simple molecules,
  like CO2 and H2O
• EX
• 6CO2(g) 6H2O(l) C6H12O6(aq) 6O2(g)
• Here glucose (sugar) is made from CO2 and H2O!

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4. DECOMPOSITION

• A reaction in which a compound is broken down
  into smaller substances is known as
  decomposition.
• EX
• CH3OH(g) CO(g) 2H2(g)
• Al2(SO4)3(s) Al2O3(s) 3SO3(g)

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5. DISPLACEMENT

• Elements trade places in displacement reactions.
• EX
• 2Al(s) 2CuCl2(aq) 2AlCl3(aq) 3Cu(s)
• See the Aluminum goes with the Chlorine now and
  the Copper is alone!
• Displacement is like finding a new dance partner!

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DOUBLE-DISPLACEMENT!Double the fun!

• Both sets of dancers have changed partners!
• Ex AB CD AD BC
• 2KI(aq) Pb(NO3)2(aq) PbI2(s) 2KNO3(aq)