Summary:
A bag of marshmallows is used to demonstrate Boyle’s Law, the relationship between pressure and volume.
Hazards:
Please don’t eat the marshmallows, dessicators aren’t pristine.
Materials:
Jet-puffed marshmallows
Vacuum pump
Vacuum desiccator
Hosing to connect vacuum to desiccator
Procedure:
Place the entire bag of marshmallows in the desiccator.
Attach the vacuum hose to the desiccator and engage the pump.
At first the marshmallows inflate, as air trapped inside the marshmallows expands, demonstrating Boyle’s law that volume increases as pressure decreases.
Whole bag allows more to see demo in large classrooms.
Whole bag can be “inflated” to fill entire vacuum chamber.
When the vacuum is first applied, the marshmallows inflate,
(Allows even the back of the room can view, and so that the space is entirely filled after vacuum).
Hint:
Discussion:
PV=nRT where T and moles trapped are constant.
As P increases, V must decrease for nRT to remain constant.
At first the marshmallows will inflate (following Boyle's law which states that pressure and volume are inversely proportional). Once all the air is pumped out, the marshmellow will suddenly deflate (due to the intermolecular forces that hold the molecules together).
To schedule a demonstration, please send an email to the demonstration lab.
Contact:
Eric Camp
Lecture Demonstration Technician
Bagley Hall 171
(206) 543-1606