Chemical Formulas and Equations Elements and Number of Atoms Matter and Energy Chemical Formulas and Equations Part I: The Big Picture What are the starting substances (molecules) in a chemical equation called? _________________________________________________________________________ What are the final or new substances (molecules) in a chemical equation called? _________________________________________________________________________ In your own words, describe what happens to the hydrogen and oxygen molecules when forming water. Something must be re-combined. How does this happen? _____________________________________________________________________________________________________________________________________________________________________ Part II: Chemical Formulas 8.5DF: Chemical Formulas and Equations Re-temlated JPh 7/31 Chemical Formula Elements and Number of Atoms Model ZnCl2 MgCO3 CuCl2 NaHCO3 CO2 1 1

Part III: Chemical Equations Chemical Formulas and Equations Matter and Energy Part III: Chemical Equations 1. H2CO3 → H2O + CO2 Reactants Products Model of Reactants Model of Products 2. 2Cu + O2 → 2CuO 3. 2Na + 2HCl → H2 + 2NaCl 4. Cl2 + 2KI → 2KCl + I2 5. Mg + 2HCl → MgCl2 + H2 2

Part III: Chemical Equations, continued Chemical Formulas and Equations Matter and Energy Part III: Chemical Equations, continued What happens to reactant molecules when forming product molecules? ____________________________________________________________________________________________________________________________________________________ What do the coefficients located before certain molecules in each chemical equation represent? ____________________________________________________________________________________________________________________________________________________ What do you notice about the elements on the reactant and product side of the equation? ______________________________________________________________________________________________________________________________________________________________________________________________________________________________ What do you notice about the number of atoms of each element on the reactant and product side of the equation?__________________________________________________________________________________________________________________________________________________________________ Part IV: The Balancing Act Zn + HCl → ZnCl2 + H2 Reactants Products Model of Reactants Model of Products 3

Part IV: The Balancing Act, continued Chemical Formulas and Equations Matter and Energy Part IV: The Balancing Act, continued Look at the chemical equations below. Determine which of these equations is balanced and which is not. First identify the type and number of atoms found on the reactant and product side of the equation. Then, circle whether the equation is Balanced or Not Balanced and then answer the questions on the next page. 2Na + O2 ➔ Na2O Balanced Not Balanced 2. 2NaNO3 ➔ 3NaNO2 + O2 Balanced Not Balanced 3. 2Al + 3Cl2 ➔ AlCl3 Balanced Not Balanced 4. 2P + 3I2 ➔ 2PI3 Balanced Not Balanced 5. 2Al + 2H3PO4 ➔ 3H2 + 2AlPO4 Balanced Not Balanced 6. H2O2 ➔ 2H2O + O2 Balanced Not Balanced 7. 2HCl + CuO → CuCl2 + H2O Balanced Not Balanced 4

CuO + 2HCl → CuCl2 + H2O Reflections and Conclusions Chemical Formulas and Equations Matter and Energy Reflections and Conclusions In your own words, explain what the Law of Conservation Mass tells us. __________________________________________________________________________________________________________________________________________________ Why is the Law of Conservation Mass important to understand when writing chemical formulas and chemical equations? _________________________________________________________________________ _________________________________________________________________________ Use the chemical equation below and all of the information learned in this Explore Activity to answer the questions below. CuO + 2HCl → CuCl2 + H2O Write down the chemical formulas of the reactants. State how many atoms of each element are on the reactant side. __________________________________________________________________________________________________________________________________________________ Write down the chemical formulas of the products. State how many atoms of each element are on the product side. __________________________________________________________________________________________________________________________________________________ How does the number of atoms present on each equation side relate to the Law of Conservation Mass? ___________________________________________________________________________________________________________________________________________________________________________________________________________________________ 5