|When you freeze a marshmallow why does it get so
hard, and then when you expose it to room
temperature it changes back to a regular
|Question Date: 2010-07-09|
Marshmallows contain sugar, water, and gelatin
and possibly other ingredients for flavoring and
sweetening. The gelatin is soaked in water to form
a gel and whipped to form the fluffy
marshmallow.Gelatin is solid at room temperature;
water is liquid. A gel is a mixture of a solid and
a liquid (soft contact lenses are an example of a
hydrogel). When you put a marshmallow in the
freezer, the water freezes even though it is part
of the gel, causing the marshmallow to become
hard. When you heat it up again, the water melts
and the marshmallow softens. However, being mixed
with the gelatin should decrease the freezing
point of the water so you have to get it colder
than usual to freeze the water. Normally water
freezes at 0 degrees C(or 32 degrees F); however
when it is mixed with other chemicals, the
hydrogen bonding network necessary to form ice is
disrupted. This causes the colligative property
known as freezing point depression.
The marshmallow, like many things, contains
water.When the water freezes, all of the water
molecules stop moving around and just "hold hands"
and vibrate in place. The object feels hard to
us. As it heats up, the molecules "let go" of
each other and move around, making the marshmallow
Not everything goes back to normal
after the water inside it freezes. If you have
ever frozen raw fruit, you have probably seen that
it gets all mushy when it thaws. That's because
the ice takes up more space than liquid water. It
bursts the cell walls that gave the fruit its
structure. So when the ice melts, the fruit is
If you melted the entire
marshmallow (not just the ice) do you think it
would go back to its old shape? Why or why not?
If you try this yourself, be careful, hot
marshmallows can burn you. Thanks for asking.
The viscosity of a material is a measure of its
resistance to flow. The viscosity of most
materials increases as the Temperature goes down.
This is because the viscosity is related to how
quickly the atoms making up a substance are
vibrating about their equilibrium positions. So
when the T falls, then the atoms vibrate more
slowly and that is ultimately related to
INCREASING the materials resistance to flow.
Marshmallows are in a semi-frozen state at room
temperature. Heat them up further and they melt
(this is why the interior of a marshmallow turns
to goo in a fire, while the outside singes and
turns brown). Cool the marshmallow down in a
freezer and it goes from being semi-frozen to
fully frozen, and return it to room temperature,
and it becomes semi-frozen again.
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