Ask A Scientist Chemistry Archive

name         Voigt
status       educator
age          20s

Question -   Hi,
We are doing a science experiment and we were wondering what affect does
extreme temperatures have on liquids such as alcohol, glycerine,cooking
oil, and corn syrup. I believe that because of the fat content in the oils
they will never freeze totally. Any insight on this matter would be great.
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I assume from the context that you are referring to temperatures colder
than room temperature. As temperature is lowered most liquids crystallize.
That is the "normal" behavior, but other things can happen. If the liquid is
cooled rapidly its viscosity will increase so rapidly that the liquid
molecules get "trapped" before they can migrate to a location in the crystal
lattice of the solid. This "trapped" liquid state is called a glass. Some
liquids for crystals some of the time, and glasses some of the time
depending upon the detailed conditions. Of the liquids you mention --
glycerin, cooking oils, corn syrup -- will all likely form glasses because
they are already rather viscous. Glycerin is a particularly interesting
example because it melts at ~14 C., but almost nobody has ever seen
crystalline glycerin because it forms a glass so readily. So the key to
glass formation is the viscosity of the liquid at the freezing point and the
cooling rate.
    You might try another experiment too. Add some food colors to water and
partially freeze the solution. You might see that the ice freezes clear and
the dye stays in the liquid. This happens because ice has a rather
complicated structure that excludes most molecules from the crystals when
water begins to freeze. Good project.

Vince Calder
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Dear Ms. Voight,

Thanks for your question. To the best of my knowledge,
almost all substances will freeze if the temperature
is lowered sufficiently (although the pressure may need to
be raised). Even 4He, which condenses to a superfluid,
will form a frozen solid if the pressure is raised by
a few MPa (megaPascals).

Alcohol surely does freeze. Ordinary ethanol has
a freezing point of -114 degrees Celsius;
methanol freezes at a higher temperature (-97.7 deg. C).
These temperatures cannot be achieved in a household
refrigerator but are not difficult to achieve in the laboratory.

Cooking oil will also freeze
if the temperature is lowered sufficiently. All fats will
freeze. The CRC Handbook gives the following
typical freezing points (individual oil samples can vary
widely from these freezing points due to differences in
composition):

SUBSTANCE     FREEZING POINT
corn oil                 - 20 deg. C
sunflower oil         - 17 deg. C
olive oil                 -   6 deg. C
sesame oil             -   6 deg. C
peanut oil                  3 deg. C
palm oil                   24.1 deg. C
coconut oil              25.1 deg. C

I hope this information is helpful.

best regards,

Dr. Topper
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