Baking soda and vinegar reaction lab
01 // Question
How does the amount of baking soda used change how much a balloon inflates when it reacts with vinegar?
A testable question names one thing you change (baking soda amount) and one thing you measure (balloon size).
02 // Variables
Independent
Amount of baking soda- 1 teaspoon
- 2 teaspoons
- 3 teaspoons
Dependent
Balloon circumference after the reaction- Circumference in cm
- Time until the balloon stops inflating
03 // Hypothesis
IF more baking soda is reacted with the same amount of vinegar, THEN the balloon will inflate to a larger size, BECAUSE more baking soda means more molecules available to react with the acid, producing more carbon dioxide gas to fill the balloon.
04 // Procedure
1. Measure the vinegar
Pour the same amount of vinegar into a bottle for each trial.
2. Load the balloon
Spoon the measured amount of baking soda into a balloon using a funnel, without letting it fall in yet.
3. Attach and lift
Stretch the balloon opening over the bottle's mouth without letting the baking soda fall in until you're ready.
4. React and time
Lift the balloon so the baking soda drops into the vinegar, and time how long the balloon keeps inflating.
5. Measure the balloon
Once inflation stops, measure the balloon's circumference at its widest point with a string and ruler.
05 // Data table
| Baking soda amount | Time to stop inflating (s) | Balloon circumference (cm) |
|---|---|---|
| 1 teaspoon | ____ | ____ |
| 2 teaspoons | ____ | ____ |
| 3 teaspoons | ____ | ____ |
Formula NaHCO₃ + CH₃COOH → CO₂ + H₂O + CH₃COONa
06 // What to expect
More baking soda generally produces a bigger balloon, since baking soda (sodium bicarbonate) and vinegar (acetic acid) react to form carbon dioxide gas, water, and sodium acetate — and more starting baking soda means more CO2 gas produced, up to the point where the vinegar itself runs out.
Past a certain amount of baking soda, adding more stops increasing the balloon size much, because the reaction is then limited by how much vinegar is available to react with it rather than by the baking soda supply.
07 // Lab notes
- Work over a tray or sink — the reaction can foam up and overflow the bottle if too much of either ingredient is added at once.
- Hold the balloon opening firmly over the bottle's neck so gas doesn't escape before filling the balloon.
- Vinegar can sting eyes — keep goggles on while pouring and mixing.
08 // Remember
A reaction needs both ingredients. Adding more of just one only helps until the other one runs out.
09 // Questions people ask
What gas inflates the balloon in the baking soda and vinegar reaction?
Carbon dioxide gas. Baking soda (sodium bicarbonate) reacts with the acetic acid in vinegar to produce carbon dioxide gas, water, and sodium acetate. The CO2 gas has nowhere else to go, so it fills the balloon and inflates it.
Why does adding more baking soda eventually stop increasing the balloon size?
Once there's more baking soda than the available vinegar can fully react with, the leftover baking soda just sits unreacted. The reaction is then limited by how much vinegar is present, not by how much baking soda was added, so the balloon stops getting bigger.
Is the baking soda and vinegar reaction reversible?
No — this is a chemical reaction that produces new substances (carbon dioxide, water, and sodium acetate) that can't simply be recombined back into baking soda and vinegar. That's a key difference from a physical change, which doesn't create new substances.