Ideal Gas Laws You Can Eat

A hands-on first-year activity using marshmallows under vacuum to introduce pressure, volume, and the ideal gas law

This activity introduces first-year students to core chemical engineering concepts—pressure, volume, and the ideal gas law—through a simple, memorable demonstration: marshmallows expanding and collapsing under vacuum. It was developed for a first-year engineering design (FYED) module and is shared here so that other instructors can replicate it freely.

The goal of this page is replication. Everything you need to run the activity yourself—materials, a data-collection template, and the 3D-printable coupler—is linked below.

A peer-reviewed write-up of this activity is in progress with ASEE and will be linked here once the conference proceedings are published.

Learning Goals

  • Give first-year students an accurate, tangible picture of what chemical engineers actually do
  • Introduce the relationship between pressure and volume (Boyle’s law) through direct observation
  • Connect a playful demonstration to foundational concepts students will revisit in thermodynamics
  • Build on FYED’s broad exposure by adding depth in a single discipline

How It Works

Marshmallows are mostly trapped air in a sugar matrix. When placed in a sealed chamber and the pressure is reduced, the trapped gas expands and the marshmallow visibly puffs up; restoring pressure collapses it. Students measure and record the change, then relate their observations back to the ideal gas law:

\[PV = nRT\]

and Boyle’s law:

\[P_{1}V_{1} = P_{2}V_{2}\]

By holding temperature and the amount of gas roughly constant, students see Boyle’s law in action: as pressure drops, volume rises.

Marshmallows under decreasing pressure in a vacuum chamber exhibiting initial swelling (pre-rupture) and subsequent contraction (post-rupture).

Replicate This Activity

Materials List

Item Notes / Suggested Source
Marshmallows (standard size) Any grocery brand; fresh marshmallows work best
Clear vacuum chamber or rigid clear container Must hold a seal; size to your group
Hand vacuum pump or small electric pump Hand pump keeps cost low and is student-operable
3D-printed coupler STL provided below — connects pump to chamber
Calipers or ruler For measuring marshmallow dimensions
Data-collection sheet Template provided below

Data-Collection Template

A pre-formatted spreadsheet for students to log pressure readings and corresponding marshmallow dimensions, with built-in columns for calculating volume change.

3D-Printed Coupler

The coupler adapts a standard hand pump to the vacuum chamber. Print in PLA or PETG; no supports required.

Step-by-Step Procedure

  1. Setup — Attach the 3D-printed coupler to the vacuum chamber and connect the pump.
  2. Baseline measurement — Measure and record the marshmallow’s dimensions at atmospheric pressure.
  3. Evacuate — Slowly reduce the pressure, pausing just before rupture to record pressure and marshmallow size. Proceed to rupture.
  4. Restore — Return to atmospheric pressure and observe the collapse.
  5. Analyze — Use the template to calculate marshmallow/gelatin volume, density, rupture pressure.

Facilitation Notes & Tips

  • Works well as a small-group activity in a FYED session
  • Fresh marshmallows respond more dramatically than stale ones
  • Encourage students to predict before they evacuate, then compare to what they observe

License & Reuse

These materials are shared so that other educators can adopt and adapt the activity. Please cite the ASEE paper (link forthcoming) if you build on this work.

References