K-12 Teaching and Learning From the UNC School of Education

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Learning outcomes

  • The students will demonstrate knowledge of the Law of Conservation of Matter by building molecules to balance equations.
  • The students will demonstrate that subscripts cannot be changed by adding entire molecules to balance the equations rather than adding single jellybeans which are the equivalent to atoms.

Teacher planning

Time required for lesson

160 minutes

Materials/resources

  • pencils
  • Each group will need a bag with four different colors of jellybeans. At least sixteen of one color, twelve of a second, eight of a third, and four of a fourth.
  • toothpicks

Pre-activities

Students will need to have a basic understanding of the Law of Conservation of Matter, what polyatomic ions are, what subscripts are and why they cannot be changed, what a coefficient is and how it is used, and the basics of chemical reactions.

Activities

  1. Provide notes for students that define the Law of Conservation of Matter which states that matter cannot be created nor destroyed, and summarizes the basic steps of balancing equations.
  2. Since this is being taught to students who are, for the majority, very concrete thinkers still, I use the jellybean lab as an introductory activity. We make equations tangible! After notes are taken, all three of the lab sheets are passed out and explained.
  3. We work through the first problem together. Explain to the students that each toothpick represents a molecule of each compound in the equation. We give each element a color, and then put the correct number of each color of jellybean on the toothpick. (For large compounds, I tell them to use a jellybean to connect two toothpicks together so it shows one molecule.) We lay the molecules on the reaction grid, and begin the process of balancing.
  4. I emphasize that in order to balance the equations, they must build more of the same kind of molecules. They cannot just add single jellybeans.
  5. Once we have worked through the first equation, I have the lab partners work on their own as I monitor progress.

Assessment

To assess the students’ knowledge of balancing equations, I use the following pieces of information:

  1. Teacher observation as they work through the lab. I check to see if students are correctly building their molecular compounds and not changing or adding subscripts by adding or removing single jellybeans, and that they are able to transfer the reaction they have created into a written format.
  2. Correctly answering the lab sheet by adding coefficients to balance the equation and not changing the subscripts.
  3. Correctly answering questions involving recognizing and balancing equations on a test at the end of the unit.

Supplemental information

Comments

This year was the first time I tried this with my eighth graders. I was afraid they would have a hard time transferring the jellybeans to the equations they had to balance. It did take them the first couple of equations to figure it out, but once they got it, they had it! Some of my visual learners would draw out the equations on their homework and test to balance the equations. It has been my most successful lab to teach concrete thinkers how to balance equations!

  • North Carolina Essential Standards
    • Science (2010)
      • Grade 8

        • 8.P.1 Understand the properties of matter and changes that occur when matter interacts in an open and closed container. 8.P.1.1 Classify matter as elements, compounds, or mixtures based on how the atoms are packed together in arrangements. 8.P.1.2 Explain...

North Carolina curriculum alignment

Science (2005)

Grade 8

  • Goal 4: The learner will conduct investigations and utilize technology and information systems to build an understanding of chemistry.
    • Objective 4.07: Identify evidence supporting the law of conservation of matter.
      • During an ordinary chemical reaction matter cannot be created or destroyed.
      • In a chemical reaction, the total mass of the reactants equals the total mass of the products.