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Types of Chemical Reactions
Movie: types of chemical reactions: http://www.youtube.com/watch?v=i-HHvx1VC_8
http://www.youtube.com/watch?v=ritaljhhk7s
Learning OutcomesIdentify, give evidence for, predict products of, and classify the following types of chemical reactions:
1. Synthesis (Combination)
2. Decomposition
3. Single Replacement
4. Double Replacement
5. Neutralization (acid/base)
6. Combustion
Vocabulary Synthesis
Decomposition
Neutralization
Single displacement
Double displacement
Combustion
A chemical change: any change in which a new substance is formed.
Evidence of a Chemical Change:
Release of energy as heat (exothermic)
Release of energy as light
Change in colour
Formation of a gas
Change in odour…
Chemical Reactions
1. Synthesis: A + B AB
2. Decomposition: AB A + B
3. Neutralization: Acid(H) + Base(OH) Salt + H(OH)
4. Single displacement: A + BC AC + B
5. Double displacement: AB + CD AD + CB
6. Combustion: AB + oxygen CO2 + H2O
Types of Chemical Reactions
A + B AB where A and B represent elements
– The elements may form ionic compounds, like…
– Sodium metal and chlorine gas combine to form sodium chloride.
2Na + Cl2 2NaCl
(c) McGraw Hill Ryerson 2007
See pages 258 - 259
Sodium added to chlorine gas
Synthesis Reactions
Synthesis reactions are also known as COMBINATION reactions.Two or more reactants (usually elements) join to form a compound.
Synthesis Reaction
Example C + O2 CO2
OO C + O O C
General: A + B AB
OTHER EXAMPLES…
1. Elements that form ionic compounds: Magnesium metal reacts with oxygen gas to form magnesium oxide.
2Mg + O2 2MgO
2. Elements that form covalent compounds: Nitrogen gas and oxygen gas combine to
form dinitrogen monoxide.
2N2 + O2 2N2O
(c) McGraw Hill Ryerson 2007
Synthesis Reactions
SYNTHESIS REACTION (iron + sulphur):http://www.youtube.com/watch?v=A5H6DVe5FAI
• Decomposition reactions are the opposite of synthesis reactions.– A compounds breaks down into two or more
products (often elements).
AB A + B where A and B represent elements
1. Ionic compounds may decompose to produce elements, like the following:
• Table salt, sodium chloride, can be broken down into sodium metal and chlorine gas by melting salt at 800ºC and running electricity through it.
• 2NaCl 2Na + Cl2(c) McGraw Hill Ryerson 2007
See page 260
Decomposition Reactions
Types: Decomposition
Example: NaCl
General: AB A + B
Cl Na Cl + Na
Types: Decomposition
Example 2HgO
O Hg
O Hg
Hg
O O Hg
+
General: AB A + B
2. Covalent compounds may decompose into elements, like the following:
• By running electricity through water, the water molecules decompose into hydrogen and oxygen gases.
• 2H2O 2H2 + O2
(c) McGraw Hill Ryerson 2007
Decomposition Reactions
DECOMPOSITION REACTION:
http://www.youtube.com/watch?v=hWiWjWHdHXM
• Single replacement reactions replace one element from a compound with another element.– A compound and an element react, and the
element switches places with part of the original compound.
A + BC B + AC where A is a metal, or
A + BC C + BA where A is a non-metal
(c) McGraw Hill Ryerson 2007
See page 261
Single Replacement Reactions
Types: Single replacement
Example: Zn + CuCl2
ZnClCl Cu +
General: AB + C AC + B
ClCl Zn Cu+
1. When A is a metal:• Aluminum foil in a solution of copper(II)
chloride produces solid copper and aluminum chloride.
• 2Al + 3CuCl2 3Cu + 2AlCl3
2. When A is a non-metal:• When fluorine is bubbled through a sodium
iodide solution, iodine and sodium fluoride are produced.
• Fl2 + 2NaI I2 + 2NaF
Single Replacement Reactions
SINGLE REPLACEMENT:http://www.youtube.com/watch?v=hKtynbVtMKc
• Double replacement reactions swap elements between 2 compounds that react together to form two new compounds.– Two compounds react, with elements switching
places between the original compounds.
AB + CD AD + CB
(c) McGraw Hill Ryerson 2007
See page 262
Double Replacement Reactions
Types: Double replacement
Example: MgO + CaS
AB + CD AD + CB
SOMg Ca
+O S
Mg Ca+
– When potassium chromate and silver nitrate react, they form a red precipitate, silver chromate, in a solution of potassium nitrate.
– K2CrO4 + 2AgNO3 Ag2CrO4 + 2KNO3
(c) McGraw Hill Ryerson 2007
silver chromate
Double Replacement Reactions
Two solutions react to form a precipitate (solid) and another solution.
Ionic solution + ionic solution ionic solution + ionic solid.
AB + CD AD + CB
DOUBLE REPLACEMENT:http://www.youtube.com/watch?v=opY3FLrPTa4
• Neutralization reactions occur when an acid (most compounds starting with H) and a base (most compounds ending in OH) react to form a salt and water.
• Neutralization reactions are a type of double replacement.
• Acid + base salt + water
HX + MOH MX + H2O where X and M are elements
(c) McGraw Hill Ryerson 2007
See page 263
Neutralization Reactions
1. Sulfuric acid is used to neutralize calcium hydroxide:• H2SO4 + Ca(OH) 2 CaSO4 + 2H2O
2. Phosphoric acid helps to neutralize the compounds that cause rust, such as iron(II) hydroxide.• H3PO4 + 3Fe(OH)2 Fe3(PO4)2 + 6H2O
(c) McGraw Hill Ryerson 2007
See page 263
Neutralization Reactions
NEUTRALIZATION:
http://www.youtube.com/watch?v=_P5hGzA6Vb0
• Combustion reactions occur when a compound or element react with oxygen to release energy and produce an oxide.– Also sometimes referred to as hydrocarbon
combustion.
CXHY + O2 CO2 + H2O where X and Y represent integers
(c) McGraw Hill Ryerson 2007
See page 264
Combustion Reactions
METHANOL + oxygen: http://www.youtube.com/watch?v=98JuJ-G1qXY&feature=related
1. Natural gas (methane) is burned in furnaces to heat homes.
CH4 + O2 CO2 + 2H2O + energy
2. An acetylene torch is used to weld metals together.
2C2H2 + 5O2 4CO2 + 2H2O + energy
3. Carbohydrates like glucose combine with oxygen in our body to release energy.
C6H12O6 + 6O2 6CO2 + 6H2O + energy
(c) McGraw Hill Ryerson 2007
Acetylene torch
Combustion Reactions
(c) McGraw Hill Ryerson 2007
.
SUMMARY OF REACTIONSMovie of five of the main reactions http://www.youtube.com/watch?v=tE4668aarck