Turn a cup, balloon, and pantry ingredients into a full scientific-method investigation. Students explore how sugar concentration changes yeast fermentation by measuring balloon circumference as a proxy for CO₂ volume.

The lab emphasizes variables, fair testing, repeated trials, graphing, and CER writing—perfect for middle school science or STEM days.

What students do

• Identify IV, DV, and controls
• Write a testable hypothesis
• Prepare five sugar solutions (0%, 1%, 3%, 5%, 10%) under constant temperature
• Collect circumference data at a fixed time window with three trials per level
• Calculate averages and create a bar graph (Average Balloon Circumference vs Sugar %)
• Construct a claim supported by evidence and reasoning using fermentation science

What’s included

• Teacher Guide: setup, pacing, safety, and background science (fermentation, enzymes, osmotic stress)
• Student Packet: step-by-step procedures and raw data tables for five sugar levels with three trials each
• Summary & Graphing Pages: average-by-percentage table, graph template, and circumference-to-volume tip
• Analysis & Model Answers: four prompts with sample class data and exemplar CER and graphing responses
• Assessment Rubric: 24-point rubric covering design, data quality, graphing, CER, and collaboration

Materials needed

Five small bottles, five identical balloons, active dry yeast, table sugar, warm water (35–40 °C), thermometer, measuring cylinder/beaker, funnel, string and ruler or flexible tape, timer, labels/marker.

Why teachers love it

• Low prep and low cost
• Clear controls make a true fair test
• Rich data for graphing and CER writing
• Flexible timing for one class period or deeper analysis

➡️ You can get this STEM as well as all my other ones in this series inside my STEM Investigations Growing Bundle. As more labs are added, the price will increase. CLICK HERE to have a look

I also have the following STEM Labs in My Store:

• Blow Cup Challenge STEM Lab
• Paper Table STEM Lab
• Pendulum STEM Lab
• Parachute STEM Lab
• Catapult STEM Lab
• Paper Airplane - Angle of Attack STEM Lab
• Bottle Flip STEM Lab
• Paper Helicopter STEM Lab
• Yeast Balloon STEM Lab
• Balloon Lift Design STEM Lab
• Candy Combustion Calorimetry STEM
• Marble Ramp: Height vs Average Speed STEM Lab
• Clean Water Filtration STEM Lab
• Beetle Genetics STEM Lab
• Adaptations by Design - Extreme Environments STEM Lab

NGSS alignment

• MS-PS2 Motion and Stability: Forces and Interactions (gravity, drag, balanced/unbalanced forces)
• MS-ETS1 Engineering Design (defining problems, testing solutions, optimizing designs)
• Science & Engineering Practices: Planning and Carrying Out Investigations;
• Analyzing and Interpreting Data; Using Mathematics and Computational
• Thinking; Engaging in Argument from Evidence
• Crosscutting Concepts: Cause and Effect; Structure and Function