Balloon in Syringe Boyle's Law

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

Categories: Gases, Particles and States of Matter, Pressure and Fluids

Alternative titles: In and Out: Demonstrating Boyle’s Law

Summary

Using balloons inside a syringe, this experiment shows how gases expand when pressure decreases and contract when pressure increases, illustrating Boyle’s law.

Procedure

Fill one small balloon with air, keeping it small enough to fit inside a syringe, then tie it off.
Fill another balloon with water to match the size of the air-filled balloon and tie it off.
Place the air-filled balloon into the syringe and insert the plunger.
With the syringe tip open, push the plunger and observe how air escapes.
Seal the syringe tip with a finger and push the plunger again, noting how the balloon contracts as pressure increases.
Pull the plunger back with the tip sealed and observe the balloon expanding as pressure decreases.
Repeat the procedure with the water-filled balloon to show that liquids do not compress like gases.
Optionally, add water inside the syringe with the air-filled balloon to see how liquid limits the plunger’s movement while still affecting the air volume.

Links

Boyle's Law Experiment - Balloon Test - Science Projects for Kids - MocomiKids:

Fun with Boyle's Law | English | Air Water Compression - Arvind Gupta:

📄 In and Out: Demonstrating Boyle’s Law - Science Buddies: https://www.scientificamerican.com/article/in-and-out-demonstrating-boyles-law/

Variations

Compare balloons filled with different gases (air vs. carbon dioxide from a soda).
Try different syringe sizes to see how compression changes.
Use warm and cold balloons to investigate whether temperature affects expansion and contraction.

Safety Precautions

Be careful when using scissors to cut balloons.
Ensure the syringe has no sharp needle attached.
Do not overfill balloons, as they may burst when compressed.

Questions to Consider

What happens to the air-filled balloon when you push the plunger with the tip sealed? (It contracts because pressure increases, reducing volume.)
What happens when you pull the plunger back with the tip sealed? (It expands because pressure decreases, increasing volume.)
Why does the water-filled balloon not change shape? (Liquids are nearly incompressible, unlike gases.)
How does this demonstration connect to how we breathe? (Expanding the chest cavity lowers pressure, drawing air in; contracting raises pressure, pushing air out.)