Sugar load: unwrap the secrets behind some of the world's wackiest candies.
* Sugar glass premiered in early action movies. Actors, instead of crashing painfully through real window glass, dove into large sheets of candy glass. When shattered, these softer and safer "windows" broke into large shards, giving an authentic broken glass effect. Today, stunt-movie windows are made of plastic and wax.
* Hershey's Kisses are named as such because the machine that makes the candy looks as if it's kissing a conveyor belt with chocolate.
* Consider the statement "Eating candy does not give you cavities." If it is true, why do those who eat a lot of candy have more cavities? (Answer: www.ipch.org/ DiseaseHealthInfo/HealthLibrary/dental/decay.html)
GEOGRAPHY Have each student select a country. Then, have them research and report on the country's unique confections.
* Grolier search term: sugar production
* For history, activities, and news about candy, visit the site of the National Confectioners Association: www.candyusa.org/
Teacher's Edition by Kathleen Heidenreich
Welcome to the most candy-crazed time of the year. Each September and October, hordes of sweet-toothed buyers bag a whopping $2 billion worth of treats! While candy comes in a variety of tastes and textures--ranging from cottony fluff to popping "rocks" and cool mints--these confections all have one thing in common: sugar. This seemingly simple ingredient is really a master of disguise. "Depending on how you process it, sugar can do a lot of different things," says Rich Hartel, a food scientist at the University of Wisconsin. "That's the key to making candy." Read on as Hartel unmasks some of sugar's sweet secrets.
Q: HOW DO YOU TURN SUGAR INTO FLUFFY COTTON CANDY?
Believe it or not, the lone ingredient in cotton candy is good old sugar. It's just dressed up with custom color and flavoring. Sugar (sucrose)--a natural plant product--is a molecule (two or more atoms joined together by a chemical bond) made up of 12 atoms of carbon, 22 atoms of hydrogen, and 11 atoms of oxygen (see diagram, right). And just like the sweet specks you heap into lemonade, cotton-candy sugar has a grainy, cubelike shape called a crystal. "At [the crystal] stage, the sugar molecules are organized very uniformly with neighboring molecules," says Hartel. "It's like a parking lot filled with perfectly neat rows of the same car." But once the sugar goes through a cotton candy machine, the crystals change form; the sucrose "parking lot" goes haywire.
The candy machine consists of a large bowl with a superhot and dizzily fast-spinning chamber in the center. This cavity also contains holes tinier than sugar crystals. As the sugar whirls inside the chamber, heat breaks the crystals' bonds, dissolving the sugar into syrup. Meanwhile, centrifugal force (force that moves an object outward from a center of rotation) spits the liquid sugar through the small holes into the surrounding bowl. These sugary streams are so fine--about 50 micrometers (one millionth of a meter) in diameter--that they solidify immediately. "The rate [at which] something cools depends on its volume (space occupied by an object)," says Hartel. "The smaller the volume, the faster it cools."
Quick cooling doesn't give the sucrose molecules time to regroup. So the strands you collect into a giant fluff aren't sugar crystals. They're actually thousands of strands of sugar glass, or sucrose molecules that solidified without structure.
Q: HOW DD THEY PACK THE FIZZ INTD POP RDCKS?
"Pop Rocks are nothing but hard, candy-coated carbon dioxide (C[O.sub.2]) gas bubbles," says Hartel. Before your mouth can experience the fizz, you need hard candy. And just like cotton candy, this begins with dissolving sugar crystals. But for this recipe, you dissolve them by heating sugar in water.
Water has a boiling point of 100[degrees]C (212[degrees]F), meaning it evaporates (turns from a liquid to a gas) at this temperature. If you keep heating water at this temperature, it just keeps evaporating. But once you add sugar, which has a melting point (temperature at which a solid changes to a liquid) of 190[degrees]C (375[degrees]F), magic happens. "With sugar molecules' influence, water will boil at a higher temperature," says Hartel. And as the heat skyrockets, more water evaporates from the sugar syrup, leaving behind a pot jam-packed with dissolved sugar. Candy makers keep an eye on the syrup's temperature because that determines a candy's texture (see thermometer, below). For example, to make hard candy, the syrup must hit between 149[degrees]C to 154[degrees]C (300[degrees]F to 310[degrees]F), called the hard-crack stage, where only 1 to 2 percent of water remains.
Quick: Time to sneak in the carbon dioxide before the syrup cools. In a special machine, the gas gets whipped into the molten (melted) sugar under a superhigh pressure (amount of force on an area) of 600 pounds per square inch (psi). "A car tire holds only about 30 psi of air," says Hartel. This sweet-and-gassy mixture then visits a pressurized cooling tube, where it hardens into sugar glass with tiny, pressure-packed C[O.sub.2] bubbles trapped inside.
Nibble a piece of pop rock, and you'll soon discover that this hard candy isn't all that tough. As the sugar glass dissolves, its hold on the gas bubbles weakens. The bubbles erupt. POP!
Q: WHY DO YOU SEE BLUE SPARKS IN YOUR MOUTH WHEN YOU CHOMP DN A WINTERGREEN LIFESAVER IN THE DARK?
This phenomenon has a name: triboluminescence (TRY-bow-loo-muh-NESS-ents). The word comes from a Greek term meaning "to rub," and a Latin word for "light." That's because, "when you rub or break certain crystals--including sugar crystals-sparks occur," says Hartel.
When you crunch on the mint, friction (rubbing force) causes the sugar crystals to break apart. Some sucrose molecules unravel, letting loose some of their negatively charged particles (electrons). But these freed particles want to be reunited with their missing parts. So like Spider Man swinging from one building to reach Mary Jane at another, the electrons leap home for the grand reunion. But like the web-slinger, the electrons encounter something in between: air.
The main ingredient in air is nitrogen. When the sugar's electrons collide with nitrogen molecules, they inject the nitrogen with jolts of energy. The nitrogen molecules begin to vibrate, and then they boot out the excess energy in the form of light. Most of this light is ultraviolet (UV) light (invisible energy waves), so you can't see much of it. The light show in your mouth is mostly due to the interaction between UV light and the mint's wintergreen flavoring. "The menthol in the wintergreen is a fluorescent molecule," says Hartel. When fluorescent material absorbs invisible energy, such as the UV light from the nitrogen molecules, it converts the energy into a visible--and eerie blue light.
DIRECTIONS: Fill in the blanks to complete the sentences.
1. Sugar is a molecule made of -- atoms of hydrogen, -- atoms of carbon, and -- atoms of oxygen. The chemical formula of sucrose is written as follows: --.
2. The chemical formula for carbon dioxide is --.
3. The boiling point of water is -- [degrees]C, or -- [degrees]F. Sugar has a melting point of -- [degrees]C, or -- [degrees]F.
4. If you rub sugar crystals together, sparks occur. This phenomenon is called --.
1. 22, 12, 11; [C.sub.12] [H.sub.22] [O.sub.11]
3. Water: 100, 212; Sugar: 190, 375
BOIL IT UP
When you dissolve sugar in boiling water to make syrup, keep a candy thermometer handy. The syrup's temperature determines its sugar concentration, which influences candy's hardness. Below shows the temperatures, and candies that result.
CARAMELIZED SUGAR STAGE
Sugar: 100 percent
Product: praline nuts
Sugar: 99 percent
Sugar: 95 percent
Sugar: 92 percent
Product: gummy candy
Sugar: 87 percent
SOFT-BALL STAGE 235[degrees]F--240[degrees]F
Sugar: 85 percent
Sugar: 80 percent
It's Your Choice
1 Sugar glass is sucrose molecules that solidified
A with a very organized structure.
B under extreme heal
C without structure.
D under high pressure.
2 The sugar-syrup temperature used to make Pop Rocks is also used to make
3 The triboluminescence of wintergreen LifeSavers does not involve
C UV light.
D sugar glass.
1.c 2. d 3. d
KA-BOOM! "Pop Rocks" were invented in 1956
FLUFFY STUFF: December 7 is National Cotton Candy Day.
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|Title Annotation:||Physical Chemistry|
|Date:||Nov 1, 2004|
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