RockCandy:
A Tasteful Example of the Second Law of Thermodynamics

Making rock candy is an example of entropy decrease that you can try in your kitchen. The basic idea is to boil some water and dump in sugar until no more will disolve. You could filter the solution or pour off the liquid into a jar. Then you hang a string into the jar and let it cool.

As the jar cools heat leaves it. So, by the second law of thermodynamics, the entropy of the solution goes down. This allows patterns to form inside the jar, and one observes this as crystals of sugar on the string.

The way to think about what happens is to think at the molecular level. The molecule surfaces are able to fit together. As the heat goes out, the molecules slow down and are able to stick together. Eventually they form a macroscopically visible crystal. If sugar seems too biological for you, use salt (NaCl) or water (H₂O) instead. These simple substances occur in the absence of organisms, but upon cooling their solutions form nice crystals.

Living organisms use exactly the same principle to grow. Extremely well characterized examples include:

• binding of nucleotides to DNA (in the presence of a DNA polymerase) to replicate DNA,
• the binding of proteins to DNA to turn on or off genes,
• nucleotide incorporation during RNA transcription by RNA polymerase,
• amino acids and tRNAs binding to tRNA synthetases,
• ribosomes binding to mRNA,
• tRNA binding to mRNA on the ribosome,
• the folding of the resulting peptide into a protein,
• binding of proteins to each other to make larger complexes such as DNA polymerase, RNA polymerase and the ribosome.
• That is, every known biochemical function involves this entropy decrease principle. Thousands of papers have been written on the subject.

Example recipies:

ROCK CANDY
2 cups water
4 cups sugar
food coloring (optional)

 Place two cups of water into a saucepan. Add four cups of sugar and stir for a minute to get as much sugar as possible to dissolve.
 Place the saucepan on the stove and turn the heat to medium-high. Stir until the sugar is dissolved. Add food coloring, if desired.
 Stir. Take the saucepan off the heat. If you're using a Rubbermaid or Tupperware container you can pour the hot liquid directly into
 it. Otherwise let the liquid cool in the saucepan; then pour into your plastic container (DO NOT use a glass container!!!!). (Larger
 crystals grow is the solution cools slowly. So, if possible, place container in a warm spot.)

 Crystals will form on the surface in a few days. Do not remove them; sink them to the bottom with a spoon.  In 7 days or so the
 bottom of the plastic container will be covered with a thick layer of sugar crystals (rock candy).  Turn the container over in the
 sink. Let the excess sugar solution drain completely. This takes about 2 hours.  When the surface of the crystals is dry, push on
 the sides and bottom of the plastic bowl and the crystals will break into chunks.  Put crystals onto wax paper and let them dry
 completely. The more they dry, the more they sparkle.

WHAT IS ROCK CANDY?
Rock Candy is the product of the further refining by recrystallization of pure cane sugar. In fact, it is the purest form of sugar available because all
impurities are excluded as the large crystals form. The crystal growth is based on the particular characteristics of sugar (sucrose)
chemistry and cannot be done with the various "sugar free" substitutes seen in the market.

HOW IS IT MADE

Rock Candy is made by a process of crystalization, the same process that produces quartz and diamonds in nature (with a different ingredient, of course). It is made by busting apart the sugar (sucrose) molecular crystal lattice and then allowing it to re-form in conditions that produce larger, purer crystals. A hot, saturated solution of cane sugar and water is poured into large tanks. Careful supervision of the cooling process produces the larger crystals which are then harvested as Rock Candy Strings, sticks, and loose crystals for packaging.

HISTORY OF ROCK CANDY
For centuries Rock Candy has been recognized as having marked therapeutic and preservative qualities. In fact, in the West, sugar was used only
as a medicine or preservative up to the middle of the 18th century when people "discovered" it made a sweet treat as well. The earliest known date that
white sugar was refined was about 200 C.E. so it is probable that the further refining into what was later known as "Sugre Candie" was at about that
time.
    There are many references to what we now call Rock Candy in literature. There are several references to it in the poems of the Persian poet
Jalal-ad-Din Rumi who lived in Turkey in the middle 1200's. One early English reference in 1584 seems to sum up the virtues of Rock Candy where
it is quoted "White sugar is not so good for phlegume, as that which is called Sugar Candie." Shakespeare in Henry IV (1596) referred to its
therapeutic value as a throat soother for long winded talkers.

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ROCK CANDY USES
Today, Rock Candy is primarily used in two ways:
as a delicious confection enjoyed by children and adults alike, and as an elegant sweetening alternative to ordinary table sugar for coffee and tea in fancy hotels and restaurants.