Conservation of Mass with Baking Soda and Vinegar

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required

Categories: Chemical Quantities and Calculations, Chemical Reactions, Measurement and Units

Alternative titles: Law of Conservation of Mass Demonstration

Summary

This experiment shows that matter is not created or destroyed in a chemical reaction. When baking soda reacts with vinegar, carbon dioxide gas inflates a balloon, and the total mass before and after the reaction remains nearly the same.

Procedure

Measure 1/4 cup of vinegar and pour it into a balloon using a funnel (hold the balloon in a beaker to make this easier).
Measure 1/4 cup of baking soda into a plastic bottle using a dry funnel.
Carefully stretch the balloon’s opening over the bottle neck without spilling the vinegar, letting the balloon hang to the side.
Weigh the entire setup (bottle, baking soda, balloon, and vinegar) and record the mass.
Lift the balloon so the vinegar pours into the bottle and reacts with the baking soda, producing carbon dioxide gas. Hold the balloon in place as it inflates.
Once the reaction stops, weigh the setup again and compare with the initial mass.

Links

Law of Conservation of Mass Lab | Open VS Closed Systems | Baking Soda and Vinegar Experiment - Science Explained:

📄 Conservation of Mass - Perkins: https://www.perkins.org/resource/conservation-mass/

Variations

Try different amounts of baking soda and vinegar to see how balloon inflation changes.
Use different sizes of bottles or balloons to explore how container volume affects the reaction.
Compare results by leaving the balloon off and allowing gas to escape—does the mass measurement still match?

Safety Precautions

Perform the experiment on a tray to contain spills.
Hold the balloon securely to prevent it from popping off the bottle.
Vinegar is mildly acidic—avoid eye contact and wash hands after use.
Adult supervision is recommended for younger students.

Questions to Consider

Why does the mass stay the same before and after the reaction? (Because matter is conserved—the gas is trapped inside the balloon instead of escaping.)
What is the gas formed in this reaction? (Carbon dioxide, produced when vinegar reacts with baking soda.)
How does this experiment support the law of conservation of mass? (The closed system shows that no matter is lost, even though it changes form.)
What would happen to the measured mass if the balloon were not used? (Gas would escape, and the final measured mass would appear smaller, giving the false impression that matter was lost.)