Chemical Reactions

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.

Conservation of Matter Activity You must wear goggles during this experiment. Follow directions carefully. Group activity rules apply.

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.

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.

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.

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.

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)

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

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.

Balancing Reactions Activity Each group will have one set of cards. Separate the cards into three groups: Numbers +, arrow, reactants, products Chemical compounds

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

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.

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!

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.

Types of Reactions

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

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

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

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

Reaction Types Demonstration Synthesis A + B  AB 2Mg + O2  2MgO Single Replacement AB + C  CB + A 2HCl + 2Zn  2ZnCl + H2

Reaction Types Demonstration Double Replacement AB + CD  AD + CB 2NaOH + CuCl2  2NaCl + Cu(OH)2 Decomposition AB  A + B 2H2O2  2H2O + O2

“Brady Bunch” Diagram Fold your paper in thirds horizontally and vertically You should have nine rectangles (like this)

“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

“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.

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

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

Identifying Reaction Types Practice 3Pb + 2H3PO4  3H2 + Pb3(PO4)2 2H2 + O2  2H2O 2NaBr + Ca(OH)2  CaBr2 + 2NaOH NH4OH  NH3 + H2O

More Practice Practice Fe + CuSO4  FeSO4 + Cu MgO + H2O  Mg(OH)2 2NaCl + Ca(OH)2  CaCl2 + 2NaOH CaCO3  CaO + CO2

More Practice Balance and Classify by Type: HF + O2  H2O + F2 NH3 + H2O  NH4OH NaI + Pb(NO3)2  PbI2 + NaNO3 NaOCl  NaCl + O2