In this balloon reaction experiment, students test how changing the amount of baking soda affects how much each balloon inflates. This experiment is part of a Science Unlocked® curriculum, which leads students to observe reactions and test how different amounts affect what happens.
This activity from The Mighty Mole kit focuses on one key idea: when you change the ratio of materials in a reaction, you change the result.
What You’ll Need
From the kit:
- Balloons (6)
- Bottles (6)
- Baking soda
- Marker
- Scale
- Tape measure
- Splint
Other items
- Vinegar
- Cup
Instructions
- Label the bottles 1 through 6 using the marker.
- Then, measure 40 mL of vinegar and pour it into Bottle 1. Repeat for all bottles, so each contains the same amount.
- Place a balloon next to each bottle and label them to match.
- Before moving on to add the variable, use the scale to measure the mass of each empty balloon and record it.
Add the Variable
- Add baking soda to each balloon using the following amounts:
- Bottle 1: 1 gram
- Bottle 2: 2 grams
- Bottle 3: 3 grams
- Bottle 4: 4 grams
- Bottle 5: 5 grams
- Bottle 6: 6 grams
- Keep each balloon paired with its matching bottle.
Make Your Predictions
Before starting the reaction, ask:
- Which balloon will inflate the most?
- How large will each balloon get?
- Will the mass or size differ between bottles?
Recording predictions helps students think about how changing one variable might affect the result.
Run the Reaction
- Attach each balloon to the mouth of its bottle without letting the powder fall in yet. Make sure the seal is tight.
- When ready, lift the balloon so the baking soda drops into the vinegar.
- Then, watch as the reaction produces gas and inflates the balloon.
- Once the balloon stops expanding, carefully remove it and tie it off to keep the gas inside.
Measure the Results
- Place each balloon on the scale to measure its mass.
- Then, use a tape measure to find the circumference of each balloon at its widest point.
- Finally, record all results and compare them across the different bottles.
Comparing Results of the Balloon Reaction Experiment
As the amount of baking soda increases, the balloons inflate differently. Some may expand more than others, while some may show smaller changes than expected. These differences give students something to compare, question, and explain.
How the Reaction Changes
When baking soda reacts with vinegar, it produces carbon dioxide gas. That gas fills the balloon and causes it to expand.
Changing the amount of baking soda changes how much gas is produced, but only up to a point. Once one ingredient runs out, the reaction can’t produce more gas, even if there’s extra of the other material.
This is called a limiting factor, and it’s a key concept in understanding chemical reactions.
Try This Next
After collecting results from the balloon reaction experiment, look for patterns:
- Did increasing the baking soda always increase balloon size?
- Was there a point where the results stopped changing as much?
- How do your results compare to your predictions?
These questions help students move from observation to explanation.
What This Teaches About Ratios
This experiment shows that chemical reactions depend on the relationship between ingredients.
By testing different ratios, students learn that changing one part of a reaction affects the entire outcome. They also see that results don’t always increase in a straight line, which leads to deeper thinking.
Within Science Unlocked, this activity is part of a larger sequence that helps students connect individual experiments to broader scientific ideas. Instead of treating each activity as separate, students learn to recognize patterns and build a stronger understanding of science over time.
