Balancing Chemical Equations

1. The definition of a chemical reaction.

   A chemical change

2. What are the indicators that a chemical reaction has occurred?

   • Change in temperature

   • Bubbling

   • Color change

   • Solid forms(this solid is called a precipitate)

   • Flame is produced

3. Define the following terms:

   1. a)  Coefficient: large numbers that show the number of molecules

   2. b)  Subscript: small numbers that show the number of atoms

   3. c)  Reactants: the number of atoms for each element in the reaction (the starting material)

   4. d)  Products: a substance that is produced and equal to the reactants in the chemical equation

   5. e)  Yields (in a chemical equation/reaction)

   6. f)  Precipitate: solid forms that are evidence that a chemical reaction has occurred

   7. g)  Law of Mass Conservation: number of atoms is unchanged from reactants to products because atoms are

      neither created or destroyed

   8. h)  Balanced equation: An equation for a chemical reaction in which the number of atoms for each element in

      the reaction is equal to the total charge of the products.

   9. i)  Unbalanced equation (skeletal equation): the number of atoms in the reactants does not equal the number

      of atoms in the products

4. How is a chemical equation written?

   HINT: Use the terms reactants, products and include the arrow (yields).

   • Make the table on the previous slide for reactants and products

   • Write down the different elements on each side of the equation (should be the same elements!)

   • Count up the number of elements currently present

   • First address elements that only occur in one place (or in more than one compound) on either side (i.e.

     carbon and hydrogen)

   • Then address elements that occur in more than one place on either side (i.e. oxygen)

5. How are the products different from the reactants?

   HINT: Focus on their physical and chemical properties.

The products are the end result of the reaction.

6. Why is the Law of Mass Conservation important in chemical reactions?

The Law of Mass Conservation is important in chemical reactions because matter cannot be created or destroyed in chemical reactions.

7. Explain what the following terms indicate: a. (s) = solid

   b. (l) = liquid
   c. (g)=gas
   d. (aq) = aqueous or dissolved in water

8. What are the 7 elements that are always diatomic?

   Hydrogen (H), Nitrogen (N), Oxygen (O), Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I).

9. Practice balancing chemical equations. You have the following resources:

   - Worksheets
   - Online link for practice - Quizziz practice
   - Kahoot practice.

10. Practice converting word equations into balanced symbolic chemical equations.

11. What do you change/manipulate when balancing a chemical equation, the subscript, or the coefficient? You change the coefficient.

12. What does the coefficient indicate?

    How many molecules are present in a formula.

13. What do the subscripts indicate?

    The number of elements that are present.