Chemical Reactions
  • Using both a wet lab and LEGO bricks students understand chemical reactions
    Using both a wet lab and LEGO bricks students understand how chemicals react

This lesson is appropriate for children ages 11 and up.

The Chemical Reactions lesson introduces students to molecules, atoms, chemical notation, and chemical compounds through an engaging hands-on wet lab, and LEGO® brick models of atoms.

This lesson is also offered as a 3-hour academic field trip LEGO Chemistry at the Edgerton Center. 

Lesson Overview

This chemistry lesson begins with students doing a wet lab in a bag. The lab is from the GEMS guide “Chemical Reactions” which uses some fairly common materials for some very uncommon reactions. Students work through combinations of all or some of the materials to determine which were responsible for particular reactions. We go over proper lab procedure for a chemistry experiment, although not lab writeup.

We next go over some vocabulary pertinent to chemistry, and chemical reactions. It is at this time that we explain that each LEGO brick represents one atom, and that different color LEGO bricks represent different elements.

We discuss molecules, mixtures and compounds. Students practice writing chemical formulas (although not equations). Finally, using the LEGO bricks, students will model the original chemical reaction from the wet lab, and can see how the atoms recombined to make new molecules.

The Chemical Reactions lesson can serve many purposes in the curriculum:

  • An exciting introduction to a chemistry unit
  • A review when beginning a unit which uses previous knowledge of chemistry
  • An enrichment lesson after the students have an initial understanding of molecules and chemical reactions
  • A culminating lesson after students have completed a chemistry unit.


Teachers can also use the Chemistry activity to supplement other subjects that students may have studied. Some additional topics include:

  • Conservation of matter: as students use the LEGO bricks, they will see that every atom of the reactants is used to create the final products.
  • Exothermic vs. endothermic reactions, or conservation of energy: the reaction of these chemicals is a surprisingly exothermic one.
Curriculum Standards

This lesson meets the following items of the Massachusetts State Frameworks for grades 6-8, Physical Sciences Strand: Elements, Compounds & Mixtures:

5. Recognize that there are more than 100 elements that combine in a multitude of ways to produce compounds that make up all of the living and nonliving things that we encounter.

6. Differentiate between an atom (the smallest unit of an element that maintains the characteristics of that element) and a molecule (the smallest unit of a compound that maintains the characteristics of that compound).

7. Give basic examples of elements and compounds.

8. Differentiate between mixtures and pure substances.

10. Differentiate between physical changes and chemical changes.


​Please see the Teacher's Guide for a complete list of materials and explanations.

Student Worksheets:


Wet Lab Materials:

  • Baking soda
  • Calcium chloride
  • Phenolsulfonphthalein (phenol red)
  • Covered test tubes or vials
  • Resealable freezer bags
  • Plastic spoons
  • 50 ml beakers or similar container
  • Splash goggles
  • Large tray (optional)
  • Chemical bin (optional)
  • Gloves (optional)


LEGO Materials:

Each kit contains the following LEGO bricks: 4 brown 2x4, 4 grey 2x4*, 4 orange 2x4*, 8 pink 2x4, 8 yellow 2x4, 8 light green 2x4, 8 green 2x4, 12 black 2x4, 36 red 2x4, 32 blue 2x4, 24 white 1x2, 4 connector pegs*

*NOTE: The connector pegs, grey bricks, and orange bricks are not used often. The pegs are very small and easily lost, thus we recommend making one “teacher box” for all the pegs, grey bricks, and orange bricks.

The Atom Key Layout Mat shows the LEGO bricks we recommend for all of the lessons. We chose these bricks because they can be used to illustrate a number of chemical and biological concepts. Their colors match those commonly used in other chemical models, though other colors may be substituted. The layout mat can also be used as an easy clean up tool to check if students have all of their bricks.

LEGO bricks can be purchased from the LEGO website, the Bricklink website, or at your local LEGO store. You might also arrange a LEGO brick donation with your local Parent Teacher Association. 

Teacher Guides and Videos

PDF icon The Chemical Reactions Teachers Guide includes list of materials, a lesson description, and suggestions for classroom use in three to four 45-minute classroom lessons.

An interactive video called "Recognizing Chemical Reactions," with Dr. Kathleen Vandiver (inventor of this lesson) and produced by BLOSSOMS can assist you in teaching this lesson. A video of the teacher's guide and a written transcript can be found here. BLOSSOMS (Blended Learning Open Source Science or Math Studies) is a collaborative initiative seeking to begin to develop a large, free repository of video modules for high school math and science classes created by gifted volunteer teachers from around the world, seeded initially by MIT faculty members and by partnering educators in Jordan and Pakistan.

This 7.5 minute Video of the Wet Lab may be useful for teachers to view prior to doing the wet lab with their students. It can also be useful to lead students though the steps. It shows the results of the optional "Part E Further Experiments" (p. 2 on student worksheet. p. 11 in teacher's guide) if the teacher does not have time to do this with the class.

Document Versions prior to June 2012

2009 Reactants and Products

PDF icon 2009 Version - Atom and Molecules Layout Mat

Contact us if you would like to learn how to use the materials at our next workshop, or if you would like to inquire about a complete classroom set of materials including LEGO bricks.

LEGO®, the LEGO logo, and the brick and knob configurations are trademarks of the LEGO group, used here with permission. ©MIT. All rights reserved.