Wednesday, Sept. 4 th : “A” Day Thursday, Sept. 5 th : “B” Day Agenda  Homework questions/collect (pg. 274: 1-6 & WS)  Quiz Sec. 8.2: “Balancing Chemical Equations”  Sec. 8.3, Day 1: “Classifying Chemical Reactions” Combustion, synthesis, decomposition  Homework: 1. Sec. 8.3 review, pg. 285: #1-4, 8b,c,f, 10a,b,e,f, Practice pg. 279: # Concept Review: “Classifying Chemical Reactions” 1-3, 6-9 only

Homework Questions  Pg. 274: #1-6  “Chemical Formulas and Equations” Worksheet  “Writing Chemical Formulas” Worksheet

Section 8.2 Quiz “Balancing Chemical Equations”  As always, you may use your guided notes and book on the quiz… May the FORCE be with you!

Diatomic Elements  Before we begin this section, remember that the following elements are diatomic and exist as molecules… H 2, O 2, N 2, F 2, Cl 2, Br 2, I 2

Sec. 8.3 “Classifying Chemical Reactions”  By classifying chemical reactions into several types, the products that are likely to form are more easily predicted.  Also, reactions of each type follow certain patterns, which will make balancing them easier.  The 5 types of reactions that are covered in this section are………….

5 Types of Chemical Reactions 1.Combustion 2.Synthesis (sometimes called combination) 3.Decomposition 4.Single Displacement 5.Double Displacement

Combustion Reactions  Combustion reaction: the oxidation reaction of an organic compound, in which heat is released. The reaction of a carbon-based compound with oxygen. Products are always carbon dioxide, CO 2, and water vapor, H 2 O. C 3 H O 2  3 CO H 2 O (Complete combustion of propane, C 3 H 8 )

Combustion Reactions  If there’s not enough oxygen present, the combustion reaction is INCOMPLETE.  Carbon monoxide, CO, and unburned carbon (soot) are produced along with CO 2 and H 2 O. 2 C 3 H O 2 2 C + 2 CO + 2 CO H 2 O (Incomplete combustion of propane, C 3 H 8 ) **Combustion reactions can be tricky to balance**

Synthesis Reaction  Synthesis Reaction: a reaction in which two or more substances combine to form a new compound. (Occasionally more than 1 product) A single compound forms from 2 or more reactants. If the reaction only has 1 product, it’s a synthesis reaction. Many times, the reactants are 2 elements or 2 small compounds. Sometimes called “combination” reactions

Synthesis Reactions Two Elements Form a Binary Compound  If the reactants are 2 elements, the only way they can react is to form a binary compound, which is composed of 2 elements.  When a metal reacts with a non-metal, an ionic compound forms and the charges on the ions can be used to predict the formula for the compound that will be formed. 2 Na + Cl 2 2 NaCl (synthesis of sodium chloride)

Synthesis Reactions Two Elements Form a Binary Compound  When 2 non-metals react, often more than one compound could form, so predicting the products of these reactions is not always easy. C + O 2 CO 2 2 C + O 2 2 CO  You will probably need more information to predict the products of these reactions and to balance them correctly.

Synthesis Reactions 2 Compounds Form a Ternary Compound  Two compounds can combine to form a ternary compound, a compound composed of 3 elements. CaO(s) + H 2 O(l)  Ca(OH) 2 (s) **(Group 1 or 2 metal oxides react w/water to form a metal hydroxide)** CO 2 (g) + H 2 O(l)  H 2 CO 3 (aq) (Some oxides of non-metals can combine w/water to produce acids)

Decomposition Reactions  Decomposition Reaction: a reaction in which a single compound breaks down to form two or more simpler substances. Decomposition reactions are the OPPOSITE of synthesis reactions - only 1 reactant A single compound breaks down, often with the input of energy, into 2 or more elements or simpler compounds

Decomposition Reactions  If your reactant is a binary compound, then the products will most likely be the 2 elements that make up the compound. 2 H 2 O(l) electricity O 2 (g) + 2 H 2 (g) (decomposition of water)

Decomposition Reactions  Compounds made up of 3 or more elements usually don’t decompose into those elements. CaCO 3 (s) heat CaO(s) + CO 2 (g) **(A metal carbonate decomposes to form a metal oxide and carbon dioxide)** **A compound with a polyatomic ion, like CO 3, will likely break down to a simpler substance, like CO 2 **

Sample Problem D, Pg. 279 Predicting Products Predict the product(s) and write a balanced equation for the reaction of potassium with chlorine.  Reactants: Potassium, K, and chlorine, Cl 2  Because the reactants are 2 elements, the reaction is most likely a synthesis reaction.  K will LOSE 1 electron to form K + and Cl will GAIN an electron to form Cl - so the formula for the product will be KCl. K + Cl 2 KCl  Lastly, balance the equation: 2 K + Cl 2 2 KCl

Additional Example Predict the product(s) and write a balanced equation for the reaction of pentane, C 5 H 12, with oxygen.  Reactants: pentane, C 5 H 12, and oxygen, O 2  Because the reactants are a hydrocarbon and oxygen, we have a combustion reaction.  Products: CO 2 and H 2 O C 5 H 12 + O 2 CO 2 + H 2 O  Lastly, balance the equation: C 5 H O 2 5 CO H 2 O

Additional Example Predict the product(s) and write a balanced equation for the decomposition of sodium chloride, NaCl.  Reactant: Sodium chloride, NaCl  Because we have 1 reactant, the reaction is a decomposition reaction. NaCl Na + Cl 2  Lastly, balance the equation: 2 NaCl 2 Na + Cl 2

Homework  Sec. 8.3 review, pg 285: 1-4, 8b,c,f, 10a,b,e,f, 12  Practice box, pg. 279: #1-4  Concept Review, “Classifying Chemical Reactions”: 1-3, 6-9  We will finish section 8.3 next time… High School Open House: Tonight, 6:30 -8:00 pm