Activity 3.2 - Observing Mealworms Eating (60 min over 2 days)

Target Student Performance

Students record data about changes in mass and BTB when mealworms eat, move, and grow and reach consensus about patterns in their data.

Resources You Provide

  • bromothymol blue (BTB) solution (less than 1 cup per group of four students
  • digital balance (1 per group of four students)
  • mealworms (10-15 grams, approximately 100-150 mealworms per group of four students)
  • plastic Petri dish (1 per group of four students)
  • sealable, 9.5 cup container (1 per group of four students)
  • small container to hold mealworms (1 per group of four students)
  • thick slice of potato (food for mealworms) (1 per group of four students)
  • (From previous lesson) 3.1 Predictions and Planning Tool for Mealworms Eating with student answers

Resources Provided

Recurring Resources


Prepare the BTB, mealworms, Petri dishes, potatoes, containers, and safety glasses for students to retrieve for their groups. Use the instructions on the BTB Information and Instructions Handout for details about how to prepare the BTB. If you plan to use the poster to record student data, print the poster before class. Print one copy of 3.2 Observing Mealworms Eating Worksheet for each student. Prepare a computer with an overhead projector to display the 3.2 Observing Mealworms Eating PPT and video. You may want to print one copy of the BTB Color Handout for each group, but this is optional.


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 Mealworms Eating PPT.


Use the class discussion to interpret how successful your students are at identifying patterns in the class data. Use the 3.2 Grading the Observing Mealworms Eating 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.

The discussions in steps 10 and 12 can be helpful for informal assessment in two ways: 1) It can help you assess your students’ skills in identifying sources of error and finding patterns in data, and 2) it can help you assess how well students identify the limits of the evidence. Do they recognize that the investigation does not fully answer the Matter Change Question or the Energy Change Question?


  • Be sure to collect results from the different groups and compare their measurements.
  • Discuss threats to accuracy of measurement.
  • Check to see if students can identify unanswered questions from the investigation.
  • To save classroom time, the mealworms could be separated from the meal bedding using a colander before the investigation starts.

  • Strategic grouping with strong speakers 
  • Read BTB handout together and call upon previous experiences
  • Have students explain aloud the experimental plan after reading it
  • Compare class data orally and on the spreadsheet

Have students develop the experimental design on their own using the tools provided. For example, students may choose to set up control treatments. For example:

  • A chamber with BTB and no mealworms or potato.
  • A chamber with a potato but no mealworms.
  • A chamber with mealworms but no potato.
Extending the Learning
  • If you have a hygrometer, consider measuring water content in the air after 24 hours.
  • Place all of the mealworms into a single container and leave overnight. Students can measure the temperature for evidence that heat energy is released.
  • Follow the same procedures to investigate other animals eating, such as crickets.