Lego Atoms and Molecules: Chemical Reactions

Kathleen Vandiver PhD, MIT Edgerton Center
Type Category
Instructional Materials
Experiment/Lab Activity , Instructor Guide/Manual , Lesson/Lesson Plan
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



This series of lessons offered by the MIT Edgerton Center gives students several opportunities to work with physical and chemical changes and chemical reactions.  The focus of this review is on the wet lab and Lego modeling of the chemical reactions. Students experiment with baking soda and calcium chloride in a bag. Then, students use Legos to build the reactants and rearrange them to form the products to prove not only the Law of Conservation of Mass but also that a chemical reaction did take place.

Intended Audience

Educator and learner
Educational Level
  • Middle School
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

MS-PS1-5 Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved.

Clarification Statement: Emphasis is on law of conservation of matter and on physical models or drawings, including digital forms, that represent atoms.

Assessment Boundary: Assessment does not include the use of atomic masses, balancing symbolic equations, or intermolecular forces.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
On page 21 of the Teacher’s Guide and the Calcium Chloride and Baking Soda Mat, students are charged with building the reactants and then rearranging them to form the products. Using this investigation along with other modeling simulations, such as the PhET balancing simulation (, will help students to further interact with the idea of the number of atoms. An additional activity to support this PE is to model the reactions using atomic model kits.

MS-PS1-2 Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.

Clarification Statement: Examples of reactions could include burning sugar or steel wool, fat reacting with sodium hydroxide, and mixing zinc with hydrogen chloride.

Assessment Boundary: Assessment is limited to analysis of the following properties: density, melting point, boiling point, solubility, flammability, and odor.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
Using a less scripted and more open-ended version of the wet lab of calcium chloride and baking soda may help students to better arrive at the conclusions and evidence a chemical reaction has occurred. As such, it might make sense to have students record data in their science notebooks before completing the student pages, which follow the script and lead directly towards conclusions.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Students are asked to observe the properties of the reactants in the bag before and after mixing. The optional further experiments offer students more opportunities to interact with this practice, especially when looking for evidence of reaction such as color change.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
To continue the specific counting of the atoms in the investigation and as mentioned above in the PE section, students could research the specific reactants and products. The number and type of atoms is discussed for other reactions, such as the vinegar and baking soda extension. Using the separation and identification of products from Appendix A in the Teacher’s Guide is important to show that the differences in reactants and products. Completing this activity is important to show that there are different substances with different properties after the reaction.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
Using the Legos to model other reactions (such as by using the link on the main page to the reactions of photosynthesis and cellular respiration) would help to strengthen students’ connection to the conservation of matter.

Resource Quality

  • Alignment to the Dimensions of the NGSS: When using a less scripted version of this lesson, the learner is engaging in all three dimensions. Using the opportunity to engage in the suggested further experimentation, in which students design their own experiments with baking soda and calcium chloride, there is a richer engagement in the three dimensions. By experimenting with chemicals and then modeling with Legos, students are given a concrete way of visualising the reaction and the connection to the Law of Conservation of Matter. Completing further modeling, such as with additional reactions or simulations such as those available at PhET (, a more rich understanding can be developed.

  • Instructional Supports: There are a plethora of resources available on this page, from the teacher and student guides to the placemats. Using the student guide for the experiments would help to support special education students and differentiate this lesson, as it is very structured. Accompanying this activity with a simulation such as the PhEt balancing simulation, either in this lesson or in following lessons, will help students to more strongly reference the atoms being conserved.

  • Monitoring Student Progress: Both in the lab sheet and discussions, there are multiple opportunities for formative assessments. Suggested questions are given for discussion points and students are given the opportunity to design their own investigations with baking soda and calcium chloride. The opportunity to model additional reactions using the same Legos to build the photosynthesis or cellular respiration reaction would help to better assess student understanding. Student reflection during the data analysis offers students the opportunity to monitor their own progress, and additional reflection and response could be completed in student notebooks to further monitor and assess student progress. This would provide students the opportunity to use a claim-evidence-reasoning paragraph answering a question, either "Did a chemical change happen in the bag?" or "Did the experiment support the Law of Conservation of Mass?"

  • Quality of Technological Interactivity: - none -