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Systems and Scale | Activity 3.4

Activity 3.4: Molecular Models for Soda Water Fizzing (40 min) 

Target Student Performance

Students use molecular models to explain how carbon, oxygen, and hydrogen atoms are rearranged into new molecules during the decomposition of carbonic acid (the chemical change that happens when soda water fizzes).

Students model the decomposition of carbonic acid (H2CO3) to carbon dioxide and water using molecular model kits. They describe this chemical change in two ways: molecular models, and a chemical equation.

Materials You Provide

  • molecular model kit (1 per pair of students )

Resources Provided


Prepare one model kit for each pair of students. Print one copy of the Molecular Models 11 x 17 Placemat and one copy of the 3.4 Molecular Models for Soda Water Fizzing Worksheet for each pair of students. Prepare a computer and a projector to display the PPT.


1. Use the instructional model to show students where they are in the course of the unit..


Listen for the students’ sense of necessity to make sure that atoms last forever during chemical changes. Asking them about the “atoms are forever” rule during the molecular modeling and animation may give you a sense of how committed they are to conserving matter.