Posters
1.
2.
3.
4.
5.
6.
7.
8.
Signs of a chemical reaction
Chemical vs. Physical reaction
Symbols used in chemical reactions
Synthesis
Decomposition
Single diplacement
Double displacement
Combustion
Journal Entry
• How were
these rocks
formed?
Signs of a chemical reaction
•
•
•
•
•
•
Production of….
Heat
Light
Gas
Precipitate (solid formed from two liquids)
Color change
The 5 Types of Reactions
We classify reactions into 5
categories so that we may more
easily predict the products.
NEXT
Synthesis Definition
Synthesis reaction – 2 substances are
combined to form a single product
• Combination reactions may also be
called composition or synthesis
reactions.
A + B  AB
+

MENU
Synthesis Examples
2Mg + O2  2MgO
Magnesium and oxygen combine to form
magnesium oxide.
2H2 + O2  2H2O
Hydrogen and oxygen combine to form
dihydrogen monoxide (water)
MENU
Synthesis Demonstration
Zinc + Sulfur  Zinc Sulfide
Zn + S  ZnS
Observations:
Decomposition Definition
Decomposition reaction – A single
compound is broken down into 2 or more
products.
AB  A + B

+
MENU
Decomposition Examples
2NaCl(s)  2Na(s) + Cl2(g)
Sodium chloride (table salt) decomposes
into sodium and chlorine gas.
CaCO3  CaO + CO2
Limestone (CaCO3 ) decomposes into lime
(CaO) and carbon dioxide.
MENU
Decomposition
2 H2O  2H2 + O2
Water decomposing into
hydrogen gas and
oxygen gas.
Decomposition of H2O2
MENU
Decomposition Demonstration
C12H22O11
+ H2SO4 → C + H2O +
SO2
(balance this!)
Sugar + Sulfuric acid  Pure carbon +
Water + Sulfur dioxide
Observations:
Decomposition Demonstration
• 2 NaHCO3 --> Na2CO3 + H2O + CO2
Observations:
Massinitial
Massfinal
Combustion Definition
Combustion reaction – Hydrogen or a
hydrocarbon (H and C) burn in oxygen to
produce water and carbon dioxide. Heat is
given off as energy.
CxHx + O2  XH2O + XCO2
MENU
Combustion Examples
CH4 + 2O2  2H2O + CO2
Methane burns in oxygen to produce water
and carbon dioxide.
C12H22O11 + 12O2  11H2O + 12CO2
A sugar molecule burns in oxygen to
produce water and carbon dioxide.
MENU
Combustion demonstration
• Ethanol + Oxygen yields Water + Carbon
dioxide
C6H12O6 + O2  H2O + CO2
Single Replacement Definition
Single Replacement reaction – A single
element takes the place of an element in a
compound.
A + BC  B + AC
+

+
MENU
Single Replacement Examples
Mg + BeO  Be + MgO
Magnesium replaces beryllium in beryllium oxide
to form magnesium oxide and beryllium.
2Na + 2HCl  H2 + 2NaCl
Sodium replaces hydrogen in hydrochloric acid to
yield hydrogen and sodium chloride.
MENU
Single Replacement Demo.
A single replacement of Zinc metal for
hydrogen in hydrochloric acid.
Zn + 2HCl  H2 + ZnCl2
Double Replacement Definition
Double Replacement reaction – Elements in
2 compounds switch places to form 2 new
compounds.
AB + CD  AD + CB
+

+
MENU
Double Replacement Examples
MgO + BeS  MgS + BeO
Oxygen and sulfur switch places to form
magnesium sulfide and beryllium oxide.
Na2S + Zn(NO3)2  2Na(NO3) + ZnS
Sulfur and nitrate switch places to form
sodium nitrate and zinc sulfide.
Make a Venn diagram
comparing….
• Synthesis vs. Decomposition
• Single replacement vs. double
replacement
What type of reaction?
• 2 H2 + O2 -- 2H20
What type of reaction?
• A + BX  AX + B
What type of reaction?
AgNO3 + CuSO4  AgSO4 + CuNO3
What type of reaction is this?
• 2 HCl (aq) + Zn (s) --> ZnCl2 (aq) + H2 (g)
What type of reaction?
Counting atoms
• How many Carbons are in each of the
following compounds:
– CO2
– C2H6
– Na(CO3)2
– Mg(C2O)4
Warm-up
• Around the room there are _7__ pictures
representing types of reactions. YOUR
pictures.
• Make a list in your notebook, 1- _7__. Try
to determine what type of reaction is being
represented by the drawing.
Definitions
• Co-efficient: The number before an
element/compound (allowed to change
when balancing)
– Ex: 2 H2
• Subscript: The small number after an
element/compound (NEVER allowed to
change when balancing
– Ex: 2 H2
Sacrificial Gummy Bear
• Demonstrates:
– Two types of chemical reactions
– HIGHLY Exothermic energy change
– Chemical energy converted into thermal,
radiant and sound energy
Chemicals used
• KClO3 - Potassium chlorate
• C12H22O11 - Sucrose
First reaction
KClO3 (s)  KCl (l) + O2
What type of reaction is this?
First reaction
KClO3 (s)  KCl (l) + O2
Is this reaction balanced? (Make an RT
table)
First reaction
KClO3 (s)  KCl (l) + O2
Balance it!
First reaction
2 KClO3 (s)  2 KCl (l) + 3 O2 (g)
First reaction
2 KClO3 (s)  2 KCl (l) + 3 O2 (g)
Second reaction
C12H22O11 + O2 (g)  C (s) + CO2 (g) + H2O (g)
What type of reaction is this?
Second reaction
C12H22O11 + O2 (g)  C (s) + CO2 (g) + H2O (g)
Is it balanced? (Make an R/P table)
If not, balance it! (1 min. early release if done
correctly!)
Second reaction
C12H22O11 + 3 O2  9 C + 3 CO2 + 11 H2O
Balanced equation
Exothermic
• Reactions which release energy
∆H = 5635 kJ
How to balance equations
• 1.) Create a “R/P” table
– (Reactants vs. Products)
• 2.) Add coefficients to create equal
numbers
• 3.) update the R/P table
• 4.) Change co-efficients until R = P
Pre-lab/practice
• Purpose: To generate hydrogen gas
– To set norms of behavior when dealing with
acid
Norms:
Locations
• Ring stands are on top of fume hood
• Clamps are in 4A
• All other materials are on counter by sink 1
Materials
•
•
•
•
Ring stand/clamp
Test tube
1-2 pea-size chunks of Zn
1 bottle of HCl
Procedure
• Set up your apparatus as demonstrated
• Add the Zinc to the test tube
• Add approximately 2-4 cm of HCl to the
test tube
• Cover with a small piece of aluminum foil
• Look for signs of a chemical reaction
• Allow to react for 3-4 minutes
Test
• Raise your hand when time has elapsed
• Use the flame test to look for signs of H2
gas
Clean up
• All test tubes must be cleaned out with
Alconox
• Make sure that all acid is flushed with a
large amount of water
• Sinks are to be totally clean
Homework reminder
• Read and take notes on pages 256-264
• Answer questions 1 and 2
• Due next class