Presentation on theme: "BALANCING EQUATIONS & CHEMICAL REACTIONS Evidence of Chemical Change Changes in Energy (E) Release of E as heat Release of E as light Production of sound."— Presentation transcript:
BALANCING EQUATIONS & CHEMICAL REACTIONS
Evidence of Chemical Change Changes in Energy (E) Release of E as heat Release of E as light Production of sound Reduction or increase of temperature Absorption or release of electrical Energy Formation of new substances Formation of a gas Formation of a precipitate Change in color Change in odor
Conservation of Mass Law of Conservation of Mass In any physical or chemical reaction, mass is neither created nor destroyed; it is conserved! Reactants Products Same number of atoms on both sides of the equation!
Balancing Equations In every balanced equation each side of the equation has the same number of atoms of each element
Important stuff! Four abbreviations are used to indicate physical states of chemicals: shown as subscripts in the chemical equation (s) = solid (l) = liquid (g) = gas (aq)= aqueous solution ( dissolved in water) Symbols over the arrow indicate the conditions of the reaction Heat Pressure Temperature Catalyst Reversible reaction
Balance this equation… NaNO 3 + CrCl 3 NaCl + Cr(NO 3 ) 3 How would you write it?
Combination Reaction or Synthesis Reaction Two or more simple substances react to form a more complicated one A + B AB Fe + S FeS
Combination Reactions We can predict the products of ionic compounds by thinking about the charge! Al (s) + O 2 (g) Cu (s) +S (s) Are there 2 possible products to this reactions How would we say these equations?
Decomposition Reaction A decomposition reaction is the opposite of a composition reaction - a complex molecule breaks down to make simpler ones. AB A + B 2 H 2 O 2 H 2 + O 2
Decomposition Reactions Harder to predict the products…always remember your diatomics. Water is often a product! HgO (s) NH 4 NO 3
Decomposition Reactions HgO (s) 2HgO (s) 2Hg (l) + O 2 (g) NH 4 NO 3 NH 4 NO 3 N 2 O+2H 2 O The only way to really know is to do the reaction!!
Single Replacement This is when one element trades places with another element in a compound. A + BC AC + B Mg + 2H 2 O Mg(OH) 2 + H 2
Single Replacement Reactions Easy to predict the products. Look at the ions… remember that a cation has to bond to an anion!! Dont forget about diatomics! Zn (s) +H 2 SO 4(aq) Na (s) +H 2 O OOPS! Did we balance them?
Single Replacement Reactions Zn (s) +H 2 SO 4(aq) Zn (s) +H 2 SO 4(aq) ZnSO 4(aq) + H 2(g) Na (s) +H 2 O Na (s) +H + OH - (l) 2Na (s) +2H + OH - (l) 2NaOH + H 2(g)
Single Replacement Reactions Reactivity of a metal makes a difference! If a metal is more reactive than the metal it is displacing a rxn will occur. If the metal is less reactive than the metal it is displacing, a rxn will not occur.
Metal Reactivity Increases down a group Decreases across a period
Brainiacs-- Metal Reactivity
Reactivity in Single Displacement Cs + KMnO 4 CsMnO 4 Will this occur?? Na + KMnO 4 NaMnO 4 + K Will this occur?
Double Replacement Reaction This is when the anions and cations of two different molecules switch places, forming two entirely different compounds AB + CD AD + CB Pb(NO 3 ) 2 + 2KI PbI 2 + 2KNO 3
Double Replacement Reactions Generally take place between two ionic compounds in aqueous solution Pb(NO 3 ) 2 + 2KI PbI 2 + 2KNO 3
Combustion Reactions A combustion reaction is when oxygen combines with another compound or element producing energy. When hydrocarbons (C ? H ? ) combust, water, carbon dioxide and energy are produced. C 10 H O 2 10 CO H 2 O + Energy Combustion of Naphthalene
Combustion Reactions Combustion of propane: C 3 H 8 + O 2 Combustion of methane: CH 4 +O 2 Combustion of butene (this one is tricky!) C 4 H 6 + O 2
Teacher Demo Extraordinaire!
What is a flame video- Science Friday what-is-a-flame.html
Recap: 5 Types of Reactions 1. Combination 2. Decomposition 3. Single Replacement 4. Double Replacement 5. Combustion
Warm Up: Predict the products, balance and classify the following reactions. Li + MgCl 2 C 6 H 12 + O 2 Ca(NO 3 ) 2 + NaOH
Types of Rxns Lab Take about 10 minutes to do the prelab questions on the lab. Most of the answers should be in your CB notes.
Warm Up- Balance the following combustion equations: C 4 H 4 + O 2 CO 2 + H 2 O C 3 H 6 + O 2 CO 2 + H 2 O C 7 H 14 + O 2 CO 2 + H 2 O
Types of Reaction Lab a. Synthesis: Mg + O 2 b. Decomposition CuCO 3 c. Single Replacement Zn + HCl d. Double Replacement PbNO 3 + KI
Finish the lab You have 20 minutes to get it done! Be sure that all your questions are answered!
Debrief Types of Rxns Lab
Types of Reaction Lab Synthesis: Mg + O 2 Did the mass of the system change after the reaction took place? Did you detect the presence of ammonia gas? Endothermic or exothermic?
Types of Reaction Lab Decomposition CaCO 3 What evidence indicates a chemical reaction. How do you know that carbon dioxide was formed? Endothermic or exothermic?
Types of Reaction Lab Single Replacement Zn + HCl What evidence did you see? What was in the little tube– how do you know? Endothermic or exothermic?
Types of Reaction Lab Double Replacement PbNO 3 + KI What evidence did you see? Endothermic or exothermic?
Work on classifying the types of reactions on your balancing WS. When you finish, you can start working on the back side of the Current Mole WS…. The front side should be complete!
Warm Up Balance and classify the following reactions: 1. Zn + H 2 SO 4 H 2 + Zn(SO 4 ) 2 2. CaCl 2 + NaNO 3 Ca(NO 3 ) 2 + NaCl 3. C 3 H 8 + O 2 CO 2 + H 2 O
You should have most of these WS done! 1. Balancing equations WS– classified rxn type 2. Mole Practice WS… Finish both of these… turn them in! Work on the Review! Due the beginning of class on Monday! Test after we go over the review!!
Warm Up Balance and classify the following reactions: 1. Na + H 2 CO 3 H 2 + Na 2 CO 3 2. NaF + Ca(NO 3)2 NaNO 3 + CaF 2 3. C 5 H 12 + O 2 CO 2 + H 2 O
Warm Up- part 2 Determine the molar mass of MgF 2 Convert 5.7 g of magnesium fluoride to moles. Convert 6.3 g of magnesium fluoride to molecules.
Warm Up Quiz 1. Determine the molar mass of Na 3 PO 4 2. How many moles in 10.6g of Na 3 PO 4 3. How many atoms in 0.50 mol Al? 4. How many atoms in 3.6 g of carbon?
Warm Up Balance and classify the following reactions: 1. K + H 3 PO 4 H 2 + K 3 PO 4 3. CH 12 + O 2 CO 2 + H 2 O