1. National Chemistry Week 2014 The Sweet Side of Chemistry! Candy
American Chemical Society
National Chemistry Week The Sweet Side of Chemistry! Candy
Newton South High School
Background for the Presenter
This fall marks the celebration of National Chemistry Week (October 19-25, 2014). ACS members celebrate NCW by holding events in schools, shopping malls, science museums, libraries, and even at rodeos! Teachers and students often create their own NCW celebrations as part of their regular science studies. Each year National Chemistry Week chooses a theme for the celebration. The theme this year is Candy: Feel Good Chemistry!
This PowerPoint presentation is designed for use by teachers or by chemists as a public outreach presentation. This presentation is a part of a set of materials from the American Chemical Society in support of National Chemistry Week. This set of slides presents some of the basic definitions and concepts dealing with candy as an example of food chemistry.
This presentation consists of text and images designed to illustrate basic science concepts in the context of candy. It may be necessary, and you are encouraged to edit and alter this presentation to make it appropriate for various groups or to fit in with existing lesson plans.

2. What is candy? and What does it have to do with chemistry?
 No matter what their age or background, the group you are presenting to will likely have a good idea about what candy is. But the second question is more to the point of this year’s NCW presentation. What does chemistry have to do with candy? As it turns out, it has everything to do with the making and enjoying of candy products.
Many people have a negative connotation for the word ‘chemistry’ or ‘chemical’. Part of our goal in this presentation and in NCW overall is to help people see how chemistry applies to their daily lives.

3. History Ancient candy was based on Honey
Sugar cane agriculture started in India in 6th century BCE
Sugar was a rare commodity for most of human history. Honey was the primary source of sweetness in pre-history. When sugar cane was discovered in Asia and southeast Asian, it was called ‘sticks that produce honey, without bees’. Sugar cane cultivation spread world wide and had a huge impact on the global economy and was one of the main drivers of the slave trade in 16th-18th centuries.
Sugar was affordable to only the wealth for decades. The Industrial Revolution radically changed how sugar was harvested and processed, making it widely available to the working class for the first time ever.
Candy only became widely available after the Industrial Revolution (1830s)
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4. Candy: a confection made with sugar (or other sweeteners) and often flavorings and fillings. Chemistry: The study of the properties of matter and the changes that can occur in matter.
It is always good to make a point at the outset of what the words we are using mean. Offer these two definitions or perhaps your own version of how you would define them. As with the previous slide, most people with have a very good idea of what candy is, but may have a harder time with an accurate definition of chemistry.
You may want to ask your audience for their definitions of these two words before you show this slide. It is always good to engage the audience in active participation, and this will also give you an idea of where they are in their knowledge of science.
It is important to note that the main ingredient of candy is sugar. To a large extent the chemistry of candy is the chemistry of sugar.
sucrose
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5. The Physical Properties of Candy Making
Molecular or Crystalline
Structure
Flavor characteristics
Melting point
Depending on your audience, it might be advisable to explain what physical and chemical properties are.
A physical property is an aspect of matter that can be observed without changing it. A chemical property is observed as the substance is transformed into another substance.
Some key physical properties of candy are their crystal structure (or lack of it), melting points (or lack of) and flavor characteristics.
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6. Types of Molecular Structure in Candy
Crystalline Solid: example-chocolate (crystalline cocoa butter) Amorphous Solid: examples-hard candy and taffy/chewy candy (sucrose solution) Soft Polymeric Solid: example-Gummy Bears or Jello (gelatin gel)
Consider handing out a sample of each type of candy was you explain their molecular structure.
The type of molecular structure in candy has a big effect on the taste and texture of the final product. Most solids in nature are crystalline at the molecular level. This means they have their atoms arranged in a regular, repeating pattern. We can see evidence of these patterns when snowflakes form or in large crystals like quartz or salt. Crystalline solids have a sharp melting point (they change from solid to liquid at a precise temperature.) The heating and cooling curves plateau at their boiling and melting points. This reflects the extra energy needed to break up the bonds in the crystals.
Crystals break along clean cleavage lines. Most candies that are crystalline have very small crystal structure. Made of the fatty acids in cocoa butter.
Hard candy is an amorphous solid, meaning it does not have crystal structure. They do not have a sharp melting point, but soften and become more viscous over a wide range of temperatures. When they break, they shatter in random pieces.
Gummi candies are natural polymersz of gelatin. They are formed in a crosslinked, 3-D network of polymer strands. This makes them soft and stretchy.
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7. Amorphous vs. Crystalline Solids
In amorphorous solids the particles do not have a regular pattern. The solid shatters into random pieces like glass.
Crystalline solids have a regular repeating pattern. The solid fractures along clean cleavage lines.
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8. Two Key Factors for Texture
Time: The longer the time allowed for growth and the slower the cooling, the larger the crystals.
How the syrup is handled when cooled down: The less disturbance, the larger the crystals.
rock candy – long time (several days) – large crystals
fudge – stirred while cooling slowly – small crystals
taffy – pulled while cooling quickly – no crystals are formed
hard candy – cooled so quickly – no crystals are formed
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9. The Importance of Temperature
Name
Temperature
Description
Candy Type
Thread °F
Syrup drips from a spoon
Candied fruit
Soft Ball °F
Ball in cold water, flattens when removed
fudge
Firm Ball °F
Stable ball, loses shape when pressed
Light caramel candy
Hard Ball °F
Holds balls shape, sticky
marshmallows
Soft Crack °F
Firm, flexible threads
Taffy
Hard Crack °F
Cracks under pressure
Lollipops
Caramel °F
Golden colored sugar syrup
pralines
Making candy is a very precise process. Most candy is composed primarily of a solution of sugar. As a sugar syrup is cooked, water boils away, the sugar concentration increases, and the temperature rises. The highest temperature that the sugar syrup reaches tells you what the syrup will be like when it cools. Making various types of candy is often just a matter of how high it is heated during production.
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10. The Chemical Properties of Candy
Flammability
Caramelization
Color change
Gas production
Most forms of candy are packed with energy and when rapidly oxidized can release an large amount of heat. This can be demonstrated by burning a marshmallow or by the rapid oxidation of gummy bears in molten potassium chlorate.
Caramelization is the partial oxidation of sugar that is widely used in cooking. As the sugar reacts it forms a characteristic brown color and nutty flavor. Volatile products are released producing the characteristic caramel flavor.
Specific sugars each have their own temperature of caramelization. Fructose is at 110° C, 230° F, Galactose 160° C, 320° F, Glucose160° C, 320° F, Maltose 180° C, 356° F, Sucrose 160° C, 320° F
As with the burning marshmallow and the caramelization of sugar, a color change accompanies these chemical changes. Sometimes chocolate will turn grey, but this is more of a physical change. If moisture accumulates on the surface inside the wrapping it can cause the sugar to dissolve. Once the moisture evaporates it leave the sugar on the surface, giving it a grey hue. It is still ok to eat, but may taste grainy.
Brittles and toffees form small amounts of acid from the browning reactions during cooking. Most recipes add a small amount of baking soda at the end of cooking. The soda reacts with the acid to make bubbles. The reaction of the baking soda and acid produces carbon dioxide gas and causes the syrup to foam. When the cooked syrup begins to harden tiny bubbles of carbon dioxide are trapped. The bubbles lighten the texture of the candy, making it easier to consume.
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11. Sugar Free Candy Sugar Alcohols, such as isomalt
High-intensity Sweeteners such as sucralose.
Sugar free candy replaces the common sugar sucrose with either sugar substitutes or artificial sugars. These compounds provide sweetness but lack the high calorie count of sucrose.
There are a number of difference alternative sweeteners available on the market, with varying degrees of ‘authentic’ sugar taste. Some of the alternative sweeteners carry side effects, such as stomach upset and diarrhea.
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12. Tasting the Shape of Molecules http://www. themolecularuniverse
The ability to taste arose through the need for organisms to sense nourishing molecules and avoid harmful ones.
Many poisonous molecules taste bitter.
Many nutritious food taste sweet.
Taste is a efficient mechanism for discriminating between molecules.
baby eating lemon
nellieblogs.blogspot.com children eating African food
girl eating sweet malt, a traditional Chinese treat

13. Tasting the Shape of Molecules http://www. themolecularuniverse
The taste of many molecules is related to their shapes and the distribution of electronic charge on their surfaces.
The essential components of the sweet taste is thought to be centered on an appropriately spaced pair of electron attracting atoms such as two oxygen atoms attached to a hydrocarbon framework.
For example, look at the structure of a sucrose molecule:
Sucrose structure from

14. Tasting the Shape of Molecules http://www. themolecularuniverse
When we taste sweet food the appropriately shaped molecules trigger receptors in taste buds.
Receptors that sense sweetness are able to tell the difference between the multitude of chemicals in common foods.
Only molecules with the correct shape will trigger the sweetness response.
Graphic from

15. Tasting the Shape of Molecules http://www. themolecularuniverse
How a sweet molecule fits into its taste receptor.

16. Tasting the Shape of Molecules http://www. themolecularuniverse
The next time that you taste a sweet food remember that receptors on your tongue are responding to a particular three dimensional arrangement of atoms and their electrons.
You will be tasting the shape of a molecule!
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17. How Are Taste and Smell Linked?
Smell and taste are closely linked. The taste buds of the tongue identify taste, and the nerves in the nose identify smell. Both sensations are communicated to the brain, which integrates the information so that flavors can be recognized and appreciated. Some tastes—such as salty, bitter, sweet, and sour—can be recognized without the sense of smell. However, more complex flavors (such as raspberry) require both taste and smell sensations to be recognized.
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18. Why Does Candy Smell Sweet?
How does our sense of smell work?
Scientists have proposed many theories about how smell works and created models corresponding to these theories.
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19. Receptor Site Theory
Receptor site theory: The currently accepted model explaining how smells are detected in the nose. Molecules fit into receptor sites that correspond to the overall shape of the molecule. This stimulates a response in the body.

20. Why Do Some Molecules Smell Sweet and Others Do Not?
Only molecules that land in receptor sites that fit the shape of the smell molecules will smell.
Must Fit Sweet Receptor
Sucrose Molecule (Sugar)
and sweet smell
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21. Inside the Nose Inside the nose is a watery mucous lining.
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22. What does polarity have to do with smell?
Polar molecules dissolve easily in other polar molecules, such as water.
Nonpolar molecules do not dissolve easily in polar molecules.
In order to smell, the molecule needs to dissolve in the water found in the mucus lining of the nose and be attracted to the receptor site.
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23. Small Nonpolar Molecules
If the molecule is symmetrical, chances are it will be nonpolar and not have a smell.
Tetrafluoromethane is symmetrical and nonpolar.

24. Small Polar Molecules
If the overall shape of a molecule is asymmetrical and the molecule is made from more than one kind of atom, chances are it is a polar molecule and will have a smell.
Chlorotriflouromethane is polar because of the chlorine atom on one side.

25. Sweet Smelling Molecules
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26. Check-in
Is this molecule polar? Does it have a smell?
This is one of the molecules that gives coffee its smell. Its name is 2-furylmethanethiol.

27. Cl- Ca2+ Cl- (repeating throughout the solid in three dimensions)
Check-in
Which of these will have a smell? Explain your reasoning.
Substance
Structure
Phase
CaCl2, calcium chloride
Cl- Ca2+ Cl- (repeating throughout the solid in three dimensions)
solid
C8H8O3, vanillin
liquid
HCN, hydrogen cyanide
gas

28. References:
Celebrating Chemistry, NCW 2014 edition: "The Sweet Side of Chemistry—Candy”, American Chemical Society, Washington D.C.
National Confectioners Association, Washington, DC 20007
The Science of Cooking, Candy, Exploratorium, Pier 15, San Francisco CA 94111,
McGee, Harold, On Food and Cooking, Simon and Schuster, 2004
Stacy, Angelica. Living By Chemistry. New York: W.H.Freeman and Co., 2012.
Husband, Tom.”The Sweet Science of Candymaking.”
Tasting the Shape of Molecules
Unilever Education Advanced Series

29. Videos to Enjoy with Your Treat
TED Talk on "How Do We Smell?”
Bytesize Science “Hard Candy Chemistry!”
Bytesize Science “Candy Corn Chemistry!”
ACS Webinar “Sweet Science: Having Fun with Candy Chemistry”
Enjoy Your Sweet Treat!
Happy National Chemistry Week 
For fun, have samples of candy and let students eat the candy while watching one or more of the videos!
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