Conservation of Mass Investigation

Erin Greenwood, Better Lesson
Type Category
Instructional Materials
Lesson/Lesson Plan , Image/Image Set , Instructor Guide/Manual , Experiment/Lab Activity
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 Better Lesson resource contains a 5E model investigation on the Law of Conservation of Mass.  The lesson begins with a discussion of the Carl Sagan quote: “The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff” and drawing an analogy to a slice of onion and our universe.  The lesson continues with a lab in which students use glow sticks and popsicles to investigate the mass of reactants and products before and after both physical and chemical changes in a closed system. Students then plan their own investigation on the conservation of mass using baking soda and vinegar.

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
This lesson serves as an introduction to this PE. The lesson begins with a more abstract model of the universe as the layers of a slice of onion to get students thinking about the esoteric concept of how we could possibly be made of starstuff and then delves deeper into measuring the mass of the contents of a glow stick before and after a chemical reaction. Drilling down from the abstract level of our universe to the big picture measurements in the investigation to the counting and modeling of atoms in this reaction helps students to understand this concept in a deeper way. While the lesson focuses mainly on the measured mass before and after the reaction, more emphasis could easily be placed on the atoms in the reactants and 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.

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
The round robin group analysis strategy allows students to engage in writing and discussion around this practice.

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 inside a glow stick. The number and type of atoms is discussed for other reactions, such as the vinegar and baking soda extension.

Crosscutting Concepts

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

Comments about Including the Crosscutting Concept
As stated above, there is a strong emphasis on mass and less emphasis on the atoms themselves. Emphasizing the atoms themselves in discussions could easily make this concept more explicit. Using molecular modeling kits would help to strengthen this connection. In addition, revisiting Sagan’s quote will also help students to connect to conservation of mass.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This lesson offers learners the opportunity to engage in all 3 dimensions. Using the phenomenon of the atoms of starstuff being part of us provides students with an anchoring phenomenon to return to with conservation of mass. Adding a video emphasizing the phenomenon may enhance learner engagement. Students experiment with conservation of mass, analyze the data from this experiment, and then design their own experimental model to demonstrate the law of conservation of mass. With added emphasis on the number and type of atoms involved, students are engaging in all 3 dimensions during this 5E lesson. The writing and discussion in the Explain portion would be a great time to add this emphasis to strengthen this lesson.

  • Instructional Supports: The investigation sheet is scaffolded for student success and could be modified to allow for more differentiation. The Claim, Evidence Reasoning Collaboration Strategy offers multiple supports for all levels of learners to support an argument with evidence. This is the point in the lesson where emphasis must be placed on the atoms themselves. Additional opportunities for counting atoms will strengthen this understanding. This collaboration offers a natural point for authentic discussion and peer feedback. The Extension Activity offers natural differentiation. 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 themselves 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 investigation using what they learned in the glow stick investigation. Student models drawn during the data analysis offer students the opportunity to monitor their own progress as other students collaborate on their models. Revisiting these models after further study would be a helpful tool for students, especially by drawing the atoms involved.

  • Quality of Technological Interactivity: - none -