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Boyle's Law


A bag of marshmallows is used to demonstrate Boyle's Law, the relationship between pressure and volume.


Please don't eat the marshmallows, desiccators have chemical residues.


  • Jet-puffed marshmallows (extra large)
  • Vacuum pump
  • Vacuum desiccator
  • Hosing to connect vacuum to desiccator


  1. Place the entire bag of marshmallows in the desiccator.
  2. Attach the vacuum hose to the desiccator and engage the pump.
  3. At first the marshmallows inflate, as air trapped inside the marshmallows expands, demonstrating Boyle’s law that volume increases as pressure decreases.
  4. Whole bag can be “inflated” to fill entire vacuum chamber.
  5. When the vacuum is first applied, the marshmallows inflate, At a certain point gasses will escape the marshmallows and they will deflate.
  6. Pull the hose off the desiccator and the marshmallow will collapse to half their original size


PV = nRT

As Pressure (P) decreases, Volume must increase for nRT to remain constant.