Chemical Reactions

1
Chemical Reactions
2
Conservation of Matter

• The law of conservation of mass says that matter
  cannot be created or destroyed.
• Even during a chemical reaction, the mass of the
  things you put in must equal the mass of the
  things that are made during the reaction.

3
Conservation of Matter Activity

• You must wear goggles during this experiment.
• Follow directions carefully.
• Group activity rules apply.

4
Group Activity Rules

• You must stay in your assigned group at your
  table unless you have permission to move around
  the room.
• No horseplay!
• Any behavior issues will result in a 0 on the
  assignment and possibly a trip to the office.

5
Conservation of Matter

• What this means is that the number of atoms of
  each element that go into a reaction must equal
  the number of atoms that come out of the reaction.

6
Conservation of Matter

• Atoms are not created or destroyed during a
  chemical reaction.
• Scientists know that there must be the same
  number of atoms on each side of a chemical
  equation.

7
Balancing Equations

• To balance a chemical equation, you must add
  coefficients in front of the chemical formulas in
  the equation.
• You cannot change or erase the subscripts.

8
Chemical Equations

• Chemical equations show us what is happening
  during a chemical reaction.
• 2Mg O2 ? 2MgO
• The elements or compound(s) on the left side are
  the reactants.
• The elements or compound(s) on the right side are
  the product(s)

9
Chemical Equations

• The coefficients show us how many of each
  molecule are reacted or produced in the reaction.
• What does the arrow mean?

10
Candy Chemistry

• We are going to look at what happens on an atomic
  level in a chemical reaction using colored
  marshmallows to represent the atoms of different
  elements and toothpicks to represent the bonds
  between atoms.

11
Balancing Reactions Activity

• Each group will have one set of cards.
• Separate the cards into three groups
• Numbers
• , arrow, reactants, products
• Chemical compounds

12
Balancing Reactions Activity

• Put the Reactants card on the left and put the
  cards for the reactant(s) below.
• Put the arrow to the right of the reactants
• Put the Products card on the right and put the
  cards for the product(s) below

13
Balancing Reactions Activity

• Count the number of atoms for each of the
  elements on the Reactants side.
• Write the symbols and numbers in the Reactants
  column in Table 1.
• Count the number of atoms for each of the
  elements on the Products side.
• Write the symbols and numbers in the Products
  column in Table 1.

14
Balancing Reactions Activity

• Use the coefficients to make the numbers of atoms
  of each element equal on both sides (balanced).
• When you have a balanced equation,
• Write the symbols and NEW numbers in the
  Reactants column in Table 1.
• Write the symbols and NEW numbers in the Products
  column in Table 1.
• HINT They should be equal!

15
Balancing Reactions Activity

• Write the balanced equation (including reactants,
  product, and correct coefficients) in the
  balanced equation column on Table 1.
• When you have the balanced equation, raise your
  hand, and I will check it off.

16
Types of Reactions
17
Partners Activity

• How are people like chemicals in reactions?
• Boy and girl are attracted to each other
• Makes a new couple (compound)
• Synthesis
• A B ? AB

18
Partners Activity

• How are people like chemicals in reactions?
• Boy and girl are no longer attracted to each
  other
• Break up (makes separate compounds)
• Decomposition
• AB ? A B

19
Partners Activity

• How are people like chemicals in reactions?
• Boy (or girl) is more attracted to another boy
  (or girl)
• One replaces the other (new compound and single
  element)
• Single Replacement
• AB C ? CB A

20
Partners Activity

• How are people like chemicals in reactions?
• Boy and girl replace each other in couples
• Two new couples (two new compounds)
• Double Replacement
• AB CD ? AD CB

21
Reaction Types Demonstration

• Synthesis
• A B ? AB
• 2Mg O2 ? 2MgO
• Single Replacement
• AB C ? CB A
• 2HCl 2Zn ? 2ZnCl H2

22
Reaction Types Demonstration

• Double Replacement
• AB CD ? AD CB
• 2NaOH CuCl2 ? 2NaCl Cu(OH)2
• Decomposition
• AB ? A B
• 2H2O2 ? 2H2O O2

23
Brady Bunch Diagram

• Fold your paper in thirds horizontally and
  vertically
• You should have nine rectangles (like this)

24
Brady Bunch Diagram

• Write Reaction Types in the middle
• Make a square with the name of each reaction type
  and leave a blank square between each one
• Synthesis
• Single Replacement
• Double Replacement
• Decomposition

25
Brady Bunch Diagram

• In the square next to each reaction type, write
  an equation or a picture of what is happening for
  that type.
• Either write the reaction type in the equation or
  picture square or draw an arrow from the reaction
  type.

26
Identifying Reaction Types

• Look at the reactants and the products
• Does the reaction have two reactants combining to
  form one product?
• Synthesis
• Does the reaction have one reactant coming apart
  to form two products?
• Decomposition

27
Identifying Reaction Types

• Look at the reactants and the products
• Does the reaction have any reactants that contain
  only one element?
• Single Replacement
• Does the reaction have two reactants made up of
  two elements switching their ions to form two
  products?
• Double Replacement

28
Identifying Reaction Types

• Practice
• 3Pb 2H3PO4 ? 3H2 Pb3(PO4)2
• 2H2 O2 ? 2H2O
• 2NaBr Ca(OH)2 ? CaBr2 2NaOH
• NH4OH ? NH3 H2O

29
More Practice

• Practice
• Fe CuSO4 ? FeSO4 Cu
• MgO H2O ? Mg(OH)2
• 2NaCl Ca(OH)2 ? CaCl2 2NaOH
• CaCO3 ? CaO CO2

30
More Practice

• Balance and Classify by Type
• HF O2 ? H2O F2
• NH3 H2O ? NH4OH
• NaI Pb(NO3)2 ? PbI2 NaNO3
• NaOCl ? NaCl O2