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Systems and Scale | Activity 3.2

Activity 3.2: Observing Soda Water Fizzing (30 min)

Students work in groups to make and record observations of soda water fizzing (mass change) and bromothymol blue (color change). Then they compare their observations with other groups and work to identify patterns and reach consensus about their results. 

Materials You Provide

  • BTB, blue (less than 1 cup per group of four students)
  • digital balance (1 per group of four students)
  • Petri dish, plastic (2 per group of four students)
  • sealable, 9.5-Cup container (1 per group of four students)
  • soda water (less than 1 cup per group of four students)
  • (Optional) Molecular modeling kits
  • (From previous activity) 3.1 Predictions Tool for Soda Water Fizzing

Resources Provided


Prepare the BTB (see instructions in the BTB Information and Instructions Handout), Petri dishes, soda water, digital balances, plastic containers, and safety glasses for students to retrieve for their groups. If you plan to use the poster to record student data, print one copy of the poster before class and post it on the wall. Print one copy of 3.2 Observing Soda Water Fizzing Worksheet for each pair of students. Prepare a computer with an overhead projector to display the PPT. Optionally, print one copy of the BTB Color Handout for each group.


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

Show Slide 2 of the 3.2 Observing Soda Water PPT.


Use the class discussion to interpret how successful your students are at identifying patterns in the class data. Use the 3.2 Assessing the Observing Soda Water Fizzing Worksheet to determine if your students had any trouble with data collection.


Addressing problems at this point as students try to find patterns in data will support their learning in future investigations. This is the first investigation, so it is likely to expose challenges that may come up again.


Have students develop the experimental design on their own using the tools provided. For example, students may choose to set up a control treatment as a chamber with BTB and no soda water.