Balancing Chemical Equations Created by Kesler Science – More 5E lessons at KeslerScience.com Presented by Kesler Science

Essential Questions: What are the different parts of the chemical equation? How can we tell if a chemical equation is balanced or not? How does balancing equation relate to the law of conservation of mass?

Quick Action – INB Template Directions for INB Template Fold the paper along the dotted line. Cut on the lines between each word up to the dotted line. Paste the blank half of the page into your INB so that the flaps open up. © KeslerScience.com

2 H2O Review Balancing Chemical Equations Subscripts describe the # of atoms in a molecule H2O Model The Coefficient represents the number of molecules 2 Molecules of H2O 2 H2O H O H O © KeslerScience.com

2H2 + O2  2 H2O Chemical Equation Balancing Chemical Equations Broken into 3 main parts Reactants Arrow = Chemical Reaction Products RAP is an easy way to remember. 2H2 + O2  2 H2O Reactants Product Arrow © KeslerScience.com

2H2 + O2  2 H2O Reactants Balancing Chemical Equations Elements or compounds which exist PRIOR to a chemical reaction 4 atoms of Hydrogen 2 atoms of Oxygen 2H2 + O2  2 H2O Reactants Students should take these notes on the INB template. © KeslerScience.com

2H2 + O2  2 H2O Products Balancing Chemical Equations New substances that are created by the rearranging of atoms after a chemical reaction 2 molecules of water 4 hydrogen atoms 2 oxygen atoms 2H2 + O2  2 H2O Product © KeslerScience.com

2H2 + O2  2 H2O Arrow/Chemical Reaction Balancing Chemical Equations The arrow represents a chemical reaction. Atoms are rearranged to form new substances Atoms are not lost or gained; they must be equal on both sides 2H2 + O2  2 H2O Arrow © KeslerScience.com

6CO2 + 6H2O  C6H12O6 + 6O2 Quick Action Work with a partner to find the following items: List the Products List the Reactants What does the arrow Represent? How many atoms of oxygen are on the product side? How many atoms of hydrogen are on the reactant side? BONUS: What process does this chemical reaction represent? Answers: C6H12O6 and O2 CO2 and H2O Chemical reaction or chemical change 18 12 © KeslerScience.com

Law of Conservation of Mass Balancing Chemical Equations Law of Conservation of Mass Matter (atoms) can neither be created  nor destroyed. Atoms can only be rearranged. © KeslerScience.com

Balancing Chemical Equations Equal number of the same type of atom on each side. If unbalanced, you can only change the coefficient to make it balanced. You CANNOT change subscripts. © KeslerScience.com

Understanding Coefficients Na + Cl2  NaCl (unbalanced) Equations without coefficients are known as skeleton equations Na + Cl2  NaCl (unbalanced) reactants product

Understanding Coefficients 2Na + Cl2  2NaCl (balanced) To illustrate the Law of Conservation of Mass, we place coefficients in equations to show that mass is not created or destroyed. 2Na + Cl2  2NaCl (balanced) reactants product Cl Na Na Cl Cl Na Na These equations are called “balanced equations” because they show the same number of elements on each side.

Yes, this equation is balanced. Understanding Coefficients You can determine whether or not equations are balanced using a simple accounting method and the skill you just learned. Is the following equation balanced? 4 Fe + 3 O2  2 Fe2O3 Reactants side Products side ___ Fe ___ 4 4 ___ O ___ 6 6 Yes, this equation is balanced.

No, this equation is not balanced. Understanding Coefficients Is the following equation balanced? Al + O2  Al2O3 Reactants side Products side ___ Al ___ 1 2 ___ O ___ 2 3 No, this equation is not balanced.

Yes, this equation is balanced. Understanding Coefficients You can determine whether or not equations are balanced using a simple accounting method and the skill you just learned. Is the following equation balanced? 2 K + 2 H2O  2 KOH + H2 Reactants side Products side ___ K___ 2 2 ___ H ___ 4 2+2 4 ___ O ___ 2 2 Yes, this equation is balanced.

No, this equation is not balanced. Understanding Coefficients Is the following equation balanced? Al4C3 + H2O → CH4 + Al(OH)3 Reactants side Products side ___ Al ___ 4 1 ___ C ___ 3 1 ___ H ___ 2 7 ___ O ___ 1 3 No, this equation is not balanced.

No, this equation is not balanced. Understanding Coefficients and Balancing Determining if an equation is balanced or not is a very simple task, but once again carelessness will cause an incorrect answer. Do NOT pretend to understand better than you really do. Make a table and get it RIGHT! Is the following equation balanced? N2 + 3O2  N2O5 Reactants side Products side ___ N ___ 2 2 ___ O ___ 6 5 No, this equation is not balanced.

Yes, this equation is balanced. Understanding Coefficients Is the following equation balanced? For some of you, it will be easier to just ignore the polyatomic ions and focus on the other elements. 2LiI + Pb(NO3)2  2LiNO3 + PbI2 Reactants side Products side ___ Li ___ 2 2 ___ I ___ 2 2 ___ Pb ___ 1 1 __2_ NO3 _2__ Yes, this equation is balanced.

Determine if the equations in your notes are balanced or not using the accounting method. 20

_____ Li _____ _____ N _____ 6 6 3 3 6 6 6 3 2 4 2 4 2 2 2 1 When you are given sets of coefficients, all you need to do is plug them in to see if they are balanced or not. Once again, this is a test of your patience more than anything else. ___Li + ___N2 ___Li3N 6 2 2 3 1 2 6 1 2 3 2 1 A 6, 2, 2 B 3, 1, 2 C 3, 2, 1 D 6, 1, 2 _____ Li _____ _____ N _____ 6 6 3 3 6 6 6 3 2 4 2 4 2 2 2 1

Determine which set of coefficients on your notes will balance the equations. 22

Always check every answer choice! When you are given a molecule to place into the equation, the same principle applies. C6H12O6 H2O2 2H2O 2CO CH4 + 2O2 CO2 + ____ _____ C _____ _____ H _____ _____ O _____ A 2CO B H2O2 C 2H2O D C6H12O6 1 7 1 1 1 1 3 1 4 12 4 4 4 4 2 4 8 4 4 4 4 4 4 Always check every answer choice!

2 Ag2O g Ag + O2 4 2 Balanced! Balancing Chemical Equations Practice Step 1 – Take Inventory of the elements and atoms on the product and reactant side. Step 2 – Is it balanced? Step 3 – If unbalanced, change coefficients until it’s balanced. 2 Ag2O g Ag + O2 4 2 Ag – 2 O – 1 4 = Ag – 1 O – 2 4 2 2 As of 2016 the Texas standards says student are to “recognize if a chemical equation is balanced using coefficients”. For your on-level classes you could stop here. It’s either balanced or it isn’t. For your advanced classes you could actually teach them how to balance the equation. Balanced! © KeslerScience.com

Quick Action – INB Template Directions for INB Template Cut the paper out along the solid line. Determine if the formulas are balanced or unbalanced. Paste the template into your INB. © KeslerScience.com

Quick Action – Balance the Equation Step 1 – Take Inventory of the elements and atoms on the product and reactant side. Step 2 – Is it balanced? Step 3 – If unbalanced, change coefficients until it’s balanced. NaBr + CaF2  NaF + CaBr2 Allow students to work with a partner Answer: 2NaBr +CaF2  2NaF + CaBr2 © KeslerScience.com

Quick Action – INB Template Directions for INB Template Cut out the INB template. Do not cut the dashed lines Paste them into your INB along the skinny tab so that the template folds up like an accordian. I would only do this sheet in your advanced class unless you have to teach HOW to balance equations rather than determining if it is balanced or not.

Check for Understanding Can you… Recognize whether a chemical equation balanced or not? Relate balanced equations to the law of conservation of mass. Clear up any confusion and answer questions. © KeslerScience.com