Conservation of Mass: The Balancing Act

NGSS Standards:

• Performance Expectation: HS-PS1-7
• Evidence Statement: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
• Science and Engineering Practice: Using Mathematics and Computational Thinking
• Disciplinary Core Idea: PS1.B: Chemical Reactions
• Crosscutting Concept: Energy and Matter

Introduction

In this task, you will explore the fundamental principle that mass cannot be created or destroyed in a chemical reaction. You will use an interactive simulation to model chemical reactions, balance equations, and mathematically prove that the number of atoms and the total mass remain constant.

Access the Simulation: Conservation of Mass Simulator

Part 1: Initial Observations

1. Open the simulation and select the “Water Synthesis” reaction from the dropdown menu.
2. Set the coefficients for all molecules (H₂, O₂, H₂O) to 1.
3. Observe the “Mass Balance Visualizer”. Is the scale balanced? Explain why or why not based on the “Reactants Mass” and “Products Mass”.
4. Look at the “Atom Inventory” table. Which elements are not balanced? How many atoms of each element are present on the reactants side versus the products side?

Part 2: Balancing the Equation

1. Adjust the coefficients in the “Reaction Equation” section until the “Check Balance” button turns green and displays “Equation is Balanced!”.
2. What are the final coefficients for the balanced equation? (H₂ + O₂ → H₂O)
3. Once balanced, record the total mass of the reactants and the total mass of the products. Are they equal?
4. Look at the “Atom Inventory” table again. Are the number of atoms for each element equal on both sides? Explain how this supports the law of conservation of mass.

Part 3: Mathematical Proof and Data Analysis

1. Select the “Methane Combustion” reaction.
2. Balance the equation.
3. Click the “Export CSV” button to download the “Atom Inventory” data.
4. Using the exported data or the table in the simulation, calculate the total mass of the reactants and the total mass of the products manually using the atomic masses provided in the simulation (H=1, O=16, C=12). Show your work.
5. Does your manual calculation match the simulation’s “Mass Balance Visualizer”?
6. Claim: Write a claim stating whether atoms and mass are conserved during the combustion of methane.
7. Evidence: Provide specific mathematical evidence from your calculations and the simulation data to support your claim. Include data on both atom counts and total mass.
8. Reasoning: Explain the scientific principles that connect your evidence to your claim. Why does the conservation of atoms necessitate the conservation of mass?