1. Balancing Chemical Reactions Making new substances

2. Main Ideas Chemical Reactions are represented by Chemical Equations. Chemical Equations are balanced to show the same number of atoms of each element on each side.The Law of Conservation of Mass says that atoms wont be created or destroyed in a chemical reaction. 3. Today you will learn how to balance a chemical equation. 4. Why? All recipes are balanced chemical reactions. The difference between a campfire and an explosion is a balanced chemical reaction. Knowing how many antacid tablets to take after eating Takis is a balanced chemical reaction 5. And The difference between:CH4 + O2 CO2 + H2Ois CH4 + 2 O2 CO2 + 2 H2O 6. Law of Conservation of Mass In a chemical reaction, matter is neither created nor destroyed. Atoms wont change their identity (e.g. a Carbon atom cant become an Iron atom)This means that you have to have the same number of each type of atom on each side of the chemical equation. Conservation of Mass Video 7. Lets learn how to do this 8. Oh No Vocabulary (but wait, you already know this) Reactants:Products:substance that takes part in and undergoes change during a reaction.substance that is formed as the result of a chemical reaction.CH4 + 2 O2CO2 + 2 H2OSubscript CoefficientIndicates a reaction has : tells taken place. Read as yields : you how many atoms you tells in a molecule. molecules have you how many If no you have. means you have subscript itIf no coefficient it means you one atom. have one molecule. 9. Balancing Equations After you write a chemical equation you have to balance it to make sure that the same number of atoms of each element are on each side. How would you balance this equation?Li + H2O H2 + LiOH 10. Steps to Balancing a Chemical EquationGet yourself an unbalanced equation.Li + H2O H2 + LiOH 11. Steps to Balancing a Chemical EquationDraw boxes around all the chemical formulas. Never, ever, change anything inside the boxes. Ever. Really. If you do, you're guaranteed to get the answer wrong.Li + H2O H2 + LiOH 12. Steps to Balancing a Chemical Equation Make an element inventory. How are you going to know if the equation is balanced if you don't actually make a list of how many of each atom you have? You won't. You have to make an inventory of how many atoms of each element you have, and then you have to keep it current throughout the whole problem.How? Use the skills you learned on counting atoms 13. Steps to Balancing a Chemical EquationLi + H2O H2 + LiOH Li H O1 2 1Li H O1 3 1 14. Steps to Balancing a Chemical EquationWrite coefficients in front of each of the boxes (molecules) until the inventory for each element is the same both before (reactants) and after products) the reaction. 15. Steps to Balancing a Chemical EquationLi + H2O H2 + LiOH Li H O1 2 1Li H OI need more hydrogens in the reactant side1 3 1 16. Steps to Balancing a Chemical EquationLi + 2 H2O H2 + LiOH Keep the inventory currentLi H O1 2 11 4 2Li H O1 3 1Oh snap, now I need more hydrogens and oxygens in the product side 17. Steps to Balancing a Chemical EquationLi + 2 H2O H2 +2 LiOH Keep the inventory currentLi H O1 2 11 4 2Li H O1 3 12 4 2Looks like we are getting somewhere, but I need more lithiums in the reactant side 18. Steps to Balancing a Chemical Equation2 Li + 2 H2O H2 + 2 LiOH Keep the inventory currentLi H O1 2 12 4 2Yay! A balanced equation.Li H O1 3 12 4 2 19. Ok, lets do this together Using the set of cards you have, replicate this equationH2 + O2H2 O 20. Inventory the atoms Write this in your sheetH2 + O2 2 2H2 O 2 1 What do I need? 21. Add a coefficient More oxygen.Inventory!H2 + O22 H2 O 2 12 2 NOT DONE! I need more hydrogen in the reactants side!4 2 22. Add another coefficient Add more hydrogen in the reactant side.2 H2 + O2 2 24 22 H2 + O2 2 H2OInventory!2 H2 O 2 14 2 NOT DONE! Check your work and write the final balanced equation 23. Your Turn. At your tables, use the cards to correctly balance the equations. Write down your answers in your in your sheets. 24. Super Saver Tips Remember to simplify. If ALL THE COEFFICIENTS share a divisor, simplify. Just like when working with fractions. If you see repeating entities such as (SO4), (PO4), (MnO4), (OH) in BOTH sides , treat them as one atom. Na3PO4 + KOH NaOH + K3PO4 Na PO4 K OH3 1 1 13 1 3 3Na PO4 K OH1 1 3 13 1 3 3Na3PO4 + 3 KOH 3 NaOH + K3PO4If you have H2O in one side and OH in the other, rewrite the water as H-OH and treat the OH (hydroxide) as one atom.