Students will investigate yeast, cellular energy use, and the characteristics of living things by comparing yeast under four different experimental conditions. Using bottles, balloons, sugar, yeast, and warm and cold water, students explore how the presence of yeast, sugar availability, and temperature affect gas production.

During the investigation, students measure changes in balloon circumference, observe bubbling and foam, and evaluate whether the results provide evidence that yeast is alive. Through controlled experimentation, quantitative data collection, graphing, analysis questions, and a structured Claim–Evidence–Reasoning (CER) response, students connect yeast metabolism, respiration, fermentation, and carbon dioxide production to the characteristics of living organisms.

Learning Targets

• Design and carry out a controlled investigation using four comparison conditions
• Explain why yeast is classified as a living, single-celled fungus
• Describe how yeast obtains and uses energy from sugar
• Connect carbon dioxide production to cellular respiration and fermentation
• Measure changes in balloon circumference as an indirect indicator of gas production
• Collect and analyze repeated measurements over time
• Calculate and compare average gas-production indicator rates
• Create and interpret a multi-line graph
• Use experimental controls to rule out alternative explanations
• Construct a CER explaining whether the results provide evidence that yeast is alive

What’s Included

Teacher Guide

Background explanations of yeast, characteristics of life, cellular energy use, respiration, alcoholic fermentation, carbon dioxide production, sugar availability, temperature, and experimental controls. Includes safety notes, investigation conditions, implementation guidance, expected results, preparation instructions, and common classroom pitfalls with practical fixes.

Student Packet

Driving question, hypothesis prompt, variables chart, pre-lab questions, step-by-step experimental procedure, temperature record, qualitative-observation space, balloon-circumference data table, rate calculations, graphing task, analysis questions, and a guided CER response.

Four Experimental Conditions

Students compare:

• Warm water + sugar + yeast
• Warm water + no sugar + yeast
• Warm water + sugar + no yeast
• Cold water + sugar + yeast

These carefully planned comparisons allow students to investigate the effects of sugar availability, yeast presence, and temperature while practicing the use of experimental controls.

Data Collection & Graphing

Students measure the change in balloon circumference at 0, 5, 10, 15, and 20 minutes. They calculate an average gas-production indicator rate for each condition and create a multi-line graph of Change in Balloon Circumference vs Time.

Balloon circumference is treated accurately as an indirect indicator of gas production, rather than a direct measurement of carbon dioxide volume.

Analysis & Answer Key

Sample balloon-circumference data, completed rate calculations, a model multi-line graph, expected observations, detailed analysis-question responses, scientific explanations, common sources of error, and a complete model CER connecting yeast activity to metabolism, carbon dioxide production, sugar availability, and temperature.

Rubric

A streamlined, one-page rubric assesses understanding of the investigation, hypothesis, setup and procedure, variables and controls, data and observations, calculations and graphing, data analysis, scientific understanding, CER writing, limitations and improvements, collaboration, and safety.

What Students Will Learn

• What desalination is and why it is used
• How a solar still separates water from dissolved salt
• How solar energy causes water to evaporate
• How water vapor condenses and is collected as freshwater
• Why dissolved salt remains in the source basin
• How to design and test a solar desalination device
• How to measure and graph freshwater production over time
• How to evaluate the efficiency of an engineering design
• How desalination can support water sustainability
• How to use Claim–Evidence–Reasoning (CER) to evaluate an engineering solution

Why Teachers Love It:

• Makes biological activity visible — students can observe bubbling, foam, and balloon inflation as yeast uses energy
• Uses four purposeful conditions to isolate the effects of yeast presence, added sugar, and temperature
• Builds core lab skills: variables, controls, measurement, data collection, calculations, graphing, and analysis
• Combines life science, cellular biology, chemistry, and scientific inquiry
• Includes quantitative measurements at repeated time intervals, not just qualitative observations
• Helps students understand the purpose of control groups and controlled variables
• Introduces the important distinction between a direct measurement and an indirect indicator
• Includes structured CER writing, error analysis, and experimental improvement
• Uses affordable, easy-to-find classroom materials
• Perfect for characteristics-of-life units, cells, metabolism, respiration, fermentation, microorganisms, or scientific-method lessons

➡️ 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

Best For

Life Science, Biology, characteristics of living things, cells, microorganisms, cellular energy, respiration, fermentation, metabolism, experimental controls, data collection, graphing, CER writing, scientific inquiry, STEM investigations, or project-based learning.

Materials Needed

Four identical 250–500 mL plastic bottles or flasks; four identical balloons; active dry or instant yeast; granulated sugar; warm water maintained near 37°C; cold water maintained near 10°C; graduated cylinder or measuring cup; digital balance or standardized measuring spoons; flexible measuring tape or string and ruler; thermometer; timer; labels; permanent marker; funnels; trays; paper towels; student packet (included).

Non-latex balloons may be used when needed.

Estimated Timing

Before Class: Prepare warm and cold water baths → portion yeast and sugar → check balloons → organize materials

Investigation Setup: Introduce the driving question → examine the four conditions → develop a hypothesis → prepare and label the treatments

20-Minute Trial: Observe yeast activity → measure balloon circumference every five minutes → record temperatures and qualitative observations

After the Trial: Calculate indicator rates → create a multi-line graph → analyze condition comparisons → complete the CER response

Allow approximately 50–60 minutes for the complete investigation. Graphing, analysis questions, and CER writing may be completed during the same class period or assigned as a follow-up lesson.

➡️ You can get this activity inside my STEM Investigations Growing Bundle.

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 Lab
• Marble Ramp: Height vs Average Speed STEM Lab
• Clean Water Filtration STEM Lab
• Beetle Genetics STEM Lab
• Adaptations by Design - Extreme Environments STEM Lab
• Newton's 1st Law of Motion STEM Lab - Penny and Index Card - Inertia Test
• Newton's 2nd Law of Motion STEM Lab - Balloon Rocket
• Newton's 3rd Law of Motion STEM Investigation - Thrust vs Nozzle Size
• Electromagnet - Coil Turns vs Magnetic Strength
• Oobleck: Force vs Flow — Non-Newtonian Fluids
• Homemade Lava Lamp - Density & Gas Production - STEM Investigation
• Passive solar water heater - STEM Investigation
• Hydroponic Food-Growing System - STEM Investigation
• Water Desalination Challenge - STEM Investigation
• Is Yeast Alive? - STEM Investigation

NGSS Alignment

MS-LS1-7 — Develop a model to describe how food is rearranged through chemical reactions that form new molecules and release energy as matter moves through an organism.

MS-PS1-2 — Analyze and interpret data about substances before and after an interaction to determine whether a chemical reaction has occurred.

This investigation also supports the Science and Engineering Practices of planning and carrying out investigations, analyzing and interpreting data, using mathematics and computational thinking, and constructing explanations from evidence.

Assessment

Use the included one-page rubric to score understanding of the investigation, hypothesis, setup and procedure, variables and controls, data and observations, calculations and graphing, data analysis, scientific understanding, CER strength, limitations and improvements, collaboration, and safety.