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Systems and Scale | Activity 4.2

Activity 4.2: Observing Ethanol Burning (30 min)

Target Student Performance

Students record data about changes in mass and BTB when ethanol burns and reach consensus about patterns in their data.

Students work in groups to make and record observations of ethanol burning (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)
  • (optional) BTB, yellow (less than 1 cup per group)
  • digital balance (1 per group of four students)
  • ethanol, 95% (10-15 ml per group)
  • large plastic container (1 per group of four students)
  • lighter (1 per group of four students)
  • Petri dish, glass (1 per group of four students)
  • Petri dish, plastic (1 per group of four students)
  • safety glasses (1 per student)
  • (Optional) Molecular modeling kits
  • (From previous activity) 4.1 Predictions and Planning Tool for Ethanol Burning with student answers

NOTE: Some classrooms have access to CO2 probes. We designed this investigation with BTB because it is less expensive than probes, but if you have them available, they are more sensitive than BTB and show changes more quickly.

Resources Provided

Recurring Resources


Prepare the BTB, Petri dishes, ethanol, lighter, digital balances, plastic containers, aluminum foil, 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 4.2 Observing Ethanol Burning Worksheet for each pair of students. Prepare a computer with an overhead projector to display the PPT and video. You may want to print copies of the BTB Information and Instructions Handout for each group, or print a few color copies of the BTB Color Handout.


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

Show slide 2 of the 4.2 Observing Ethanol Burning PPT.


Use the class discussion to interpret how successful your students are at identifying patterns in the class data. Use the 4.2 Grading the Observing Ethanol Burning Worksheet to determine if your students had any trouble with data collection.

During this Activity, note students' success in measuring changes in mass and BTB. Also note students' ability to reach a consensus about patterns in data and how they interpret results.