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In this activity students will form ionic compounds and covalent compounds using clues and questions. Students are going to then develop their own stoichiometric problems and have other groups attempt to solve it.

Grade Level

High School


By the end of this activity, students should be able to

  • Predict ionic charges
  • Predict ionic bonds
  • Predict covalent bonds
  • Solve stoichiometric problems for limiting and excess reactants.

Chemistry Topics

This activity supports students’ understanding of

  • Molecules & Bonding
  • Ions
  • Ionic Bonds
  • Covalent Bonds
  • Naming Compounds
  • Molecular Formulas
  • Chemical Reactions
  • Classification of Reactions
  • Stoichiometry
  • Limiting Reactant


Teacher Preparation: 30 minutes

Lesson: Two—90 minute class periods


  • QR code questions (1 for each question taped around the school building or classroom)
  • Paper and pen (each student)
  • Colored cardstock (for groups to write stoichiometry problems on)
  • Markers/colors/pencils


  • No specific safety precautions need to be observed for this activity.

Teacher Notes

  • You will need a QR code generator
  • Teacher will need to create 30 to 40 QR codes with questions on them scattered throughout the school building or classroom.
  • Examples of questions:
    • What type of ion gains electrons and has a negative charge? (anion)
    • What type of bond involves a sharing of valence electrons? (covalent)
    • What is the correct chemical formula and name when a calcium ion transfers electrons with a nitrate polyatomic ion to form a compound? (Ca(NO3)2 calcium nitrate)
  • Students will be in pairs, one in each pair needs a smart phone with a downloaded QR code reader app (ex: QR reader for Iphone)
  • Questions will range from naming ions (monoatomic & polyatomic) and covalent compounds to predicting the product of reactions.
  • Students should have a background in naming ions, compounds, charges, and chemical reaction types.
  • Students will keep track of their answers on a separate sheet of paper (they should also make sure to copy down the question)
  • The next day in class (another 90 minute class interval) (teacher should put students in groups of 3-4) groups will write ionic or covalent chemical reactions that they encounter in their everyday lives (students should have internet access)
  • Each group will create a question and answer key for the rest of the class
  • Questions should include:
    • Predicting the product and labeling the type of reaction
    • Creating a stoichiometric word problem and scenario for their classmates to answer
    • Groups will go around the room and answer other groups questions and compare results (questions should be hung on the board or wall so students can have access)

For the Student


Chemical reactions occur all around us. There are multiple types of reactions that involve different types of elements. Ionic and covalent bonds are two types of bonds that can be involved in chemical reactions. You have learned about how electrons are either shared or transferred in bonds. You will now predict how elements bond and why in chemical reactions. You will also see how limiting and excess reactants determine the amount of product available.

Pre-lab Questions

  1. What is an ionic bond?
  2. What is a covalent bond?
  3. What are the five major types of chemical reactions? Write the skeletal reactions.

  4. How can you predict the charges of ions?
  5. What is a cation? Anion?
  6. What is a limiting reactant? Excess reactant?


How can the conservation of mass be explained using stoichiometry?


  • Day 1:
    • In partners, using a QR reader on a smart phone or Ipad, search for the 30 hidden QR code questions.
    • Copy each question and answer the question on the student response sheet.
  • Day 2:
    • In groups, using a laptop, research some of the chemical reactions you encountered the class before, see if any are ones that you might see in your everyday life. For example:
      • Baking soda and vinegar reaction
      • Combustion of propane
      • Rusting of iron
      • Decomposition of water into oxygen and hydrogen
    • In your group, write a question and answer key. Your question for the class should include:
      • A stoichiometry word problem scenario (Get creative!)
      • An unbalanced chemical reaction (JUST THE REACTANTS)
      • Questions about limiting reactant and excess reactant
    • With your group you will go around the class and try to solve other groups stoichiometry problems.


  1. Why is the law of the conservation of mass important in dealing with chemical reactions?
  2. Why is it important to use the limiting reactant in determining the amount of product produced?
  3. Go back to your own stoichiometric problem, how much product would be produced if you did the same calculations using the excess reactant?
    • Why doesn’t this support the law of conservation of mass?
  4. Are covalent synthesis reactions predicted differently than ionic synthesis reactions? Why? Give an example of each and explain.


How can the conservation of mass be explained using stoichiometry? Why is it important to think about when you perform stoichiometric problems? When we cook we use a recipe. Can we apply this same knowledge when determining the outcome of our dish?

Student Response Sheet

Question #