|Why does low pressure make marshmallows expand?
|Question Date: 2005-11-22|
Because the bubbles of gas inside the marshmallow
try to expand. The higher pressure inside the
marshmallow pushes out when the pressure outside
Marshmallows are mostly made of air, which is a
gas.Gases expand and contract when the pressure
changes. Under high pressure, gases can be
compressed. Conversely, gases expand under low
pressure. An example is helium in a helium tank
(you know, the kind you use to blow up
balloons.The tank can hold a lot of helium gas
because the gas is kept at a high pressure. Once
the helium is released into the air it expands and
takes up more space than it did inside the tank.
Hope this helps.
Because the air bubble trapped inside the
marshmallows expand in response to the lower
pressure. This also explains why your ears hurt
when you take off in an airplane. The air
pressure's lower at altitude, so the air in your
middle ear swells like a little balloon, causing
They're full of air (like Styrofoam), and the low
pressure means that the difference in pressure
between the air inside the marshmallow and the air
outside is such that the air inside exerts a
greater pressure, puffing the marshmallow out.
Marshmallows are full of very small air bubbles.
(The walls of the air bubbles are made of sugar
and gelatin, which is pretty good at holding its
shape but is also flexible.) If you have a good
magnifying glass, you can see the bubbles. These
air bubbles are filled with air of the same
pressure as the air around them when they were
made. If a marshmallow is under normal air
pressure, the air on the inside and the air on the
outside of the bubbles pushes with the same force.
If you lower the pressure around the marshmallow
(say by putting it in a vacuum pump chamber), the
air outside the bubbles pushes less than the air
on the inside. Because the bubble walls are made
of flexible gelatin and sugar, the higher pressure
on the inside is able to push the walls of the
bubbles out -- making bigger bubbles. All the
larger bubbles lead to an expended marshmallow.
You can cause a similar effect by putting a
marshmallow in a microwave or heating it over a
fire. In that case, the heating causes the air
pressure in the bubbles to increase and the
bubbles expand.Have fun experimenting more with
marshmallows and don't forget to eat the results.
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