1. 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

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

3. 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

4. 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 ➔ 3NaNO O2 Balanced Not Balanced
3. 2Al Cl2 ➔ AlCl3 Balanced Not Balanced
4. 2P I2 ➔ 2PI3 Balanced Not Balanced
5. 2Al H3PO4 ➔ 3H AlPO4 Balanced Not Balanced
6. H2O2 ➔ 2H2O + O2 Balanced Not Balanced
7. 2HCl + CuO → CuCl2 + H2O Balanced Not Balanced 4

5. 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