Physics: The Science of

Week 05/25/20

Reading: ● Annotate the article: Ice, Cream, and Chemistry ​ ○ Underline important ideas ○ Circle important words ○ Put a “?” next to something you want to know more about ○ Highlight any topics that are related to physics

Activity: ● Make Ice Cream in a Bag at Home ○ Homemade Ice Cream Directions

Writing: ● Read the article: Inventing the longer-lasting popsicle ​ ○ Answer the writing prompt at the end of the article.

Física: La Ciencia del Helado

Semana 05/25/20

Lectura: ● Anote el artículo: Ice, Cream, and Chemistry ​ ○ Subráye ideas importantes ○ Circúle palabras importantes ○ Ponga un "?" junto a algo que usted quiera saber más ○ Resalte los temas relacionados con la física

Actividad: ● Hace helado en una bolsa en la casa ○ Homemade Ice Cream Directions

Escritura de la: ● Lea el artículo: Inventing the longer-lasting popsicle ​ ○ Responda la pregunta al fin del artículo.

ICE,Cream... Chemistryand By Brian Rohrig

here is To get an idea brands. One side effect of adding perhaps of the effect of a lot of air to ice cream is that it no fonder air on ice cream, tends to melt more quickly than childhood think of whipped ice cream with less air. memoryT than the local cream. If you whip The amount of air also has a ice cream truck driving air into cream, you get huge effect on the density of through the neighborhood, whipped cream. Whipped the ice cream. A gallon (3.8 music blaring from its tinny speak- cream has a different texture liters) of ice cream must weigh ers, beckoning all to partake of its frosty and taste than plain cream. Plain cream at least 4.5 pounds, making delights. But ice cream is not just for kids. tastes sweeter than whipped cream. Just the minimum density 0.54 U.S. residents consume 1.5 billion gallons like ice cream without air, pure cream has a gram per milliliter (or 540 of ice cream each year; that’s roughly 5 gal- sickly, overly sweet taste. This is because the grams per liter). Better brands lons (19 liters) per person! The ice cream we structure of a substance can have a big effect have higher densities—up to 0.9 all enjoy is the result of years of experimenta- on how it tastes. The structure often controls grams per milliliter. The next tion involving—you guessed it—chemistry! the rate at which flavor molecules are released time you visit a grocery store, into the mouth. The larger the structure (of compare cheaper and more Air is important! ice cream, in this case), the longer it takes expensive brands by holding for flavor molecules to be released. Flavor a container in each hand—you If you have ever made ice cream, you molecules trigger receptors on the mouth and should be able to notice a differ- already know what goes into it, ingredients tongue. ence. Then read the net weight on the such as milk, cream, and sugar. But there is The amount of air added label to confirm your one main ingredient that you may not have to ice cream is known as observation. Due to thought about, probably because you can’t see overrun. If the volume of the high fat content it—air. ice cream is doubled by of ice cream, however, Why is air so important? If you have ever adding air, then the over- and because fat is less had a bowl of ice cream melt, and then refroze run is 100%, which is dense than water, any it and tried to eat it later, it probably did not the maximum allowable ice cream will always be taste very good. If you set a whole container of amount of air that can be less dense than any aque- ice cream on the table and let it melt, the vol- added to commercial ice ous solution. Otherwise, ume of the ice cream would simply go down. cream. The less expensive El ect ro Fr ee z e /H.C. Duk & Son, LL C you would not be able to Air makes up between 30% and 50% of the brands usually contain The amount of air, known as overrun, in make root beer float! the dish of soft-serve ice cream on the left i st o c k. m , p h t s . sh u tte r k total volume of ice cream. more air than the premium is 65%, versus 35% on the right. Ice cream is an emul-

6 Chemmatters | February/march 2014 www.acs.org/chemmatters sion—a combination of two liquids that do fat, which gives it a velvety, rich texture. not normally mix together. Instead, one of Reduced-fat ice cream does not taste as the liquids is dispersed throughout the other. good as the real thing, and tends to lack the In ice cream, liquid particles of fat—called fat creamy texture. Although fat is frequently vili- globules—are spread throughout a mixture of fied, it has its purpose. Most foods that taste water, sugar, and ice, along with air bubbles delicious probably contain fat. Fat fills you up, (Fig. 1). If you examine ice cream closely, you so you don’t have to eat as much to feel full. can see that the structure is porous. A typical The problem with using fat as an ingredient air pocket in ice cream will be about one-tenth in any food is that it does not mix well with a p h o t s . c m of a millimeter across. The presence of air A close look at ice cream shows its porous lot of other substances. Fat is nonpolar, mean- means that ice cream is also a foam. Other structure. ing positive and negative charges within the fat molecule are equally dispersed. A polar substance, such as water, has separate regions of positive and negative charges—one end of a polar molecule has a partial positive charge, and the other end has a par- tial negative charge. Polar and non- polar substances do not mix. Just like oil floats to the top of water, the fat content of ice cream has a tendency to separate out, as well.

Keeping it all together Because ice cream is an emulsion, you would expect that the fat droplets that are present in the mixture would ry en a h ew separate after some time, similar to a bottle of salad dressing in which the oil separates from the rest of the Figure 1. Some of the most common ingredients in ice cream include ice crystals, air, fat globules, dressing. When you shake a bottle of sugar (sucrose), and flavoring agents (such as vanillin). salad dressing, the two parts come examples of foams are whipped taste sickly sweet. In parts of the world where together. But after a few minutes, they begin cream, marshmallows, and soft drinks are normally consumed warm, to separate. That’s because the oil droplets meringue (as in lemon meringue there is less added sugar. If these same soft interact with one another, a process called pie). drinks were served cold, they would not taste coalescence. sweet enough. In the case of milk, each fat droplet is Sugar and fat A big reason why ice cream tastes so good coated with a layer of milk proteins that pre- is because of its high fat content. Unless it is vents the fat droplets from interacting with Milk naturally contains lactose, labeled as light, low-fat, or non-fat ice cream one another. These milk proteins act as “emul- or milk sugar, which is not very must contain at least 10% fat, and this fat sifiers”—substances that stabilize emulsions sweet. Ice cream makers need to add a must come from milk. (You and allow the liquid droplets lot more sugar than you probably real- cannot use lard when mak- present in the emulsion to ize—usually, sucrose or glucose. Cold ing ice cream!) Before milk remain dispersed, instead of tends to numb the taste buds, making is homogenized, a thick clumping together. Because them less sensitive. So, more sugar needs layer of cream rises to the these milk proteins have a to be added to produce the desired effect at top. This cream has a high- nonpolar side, and because

the low temperatures at which ice cream is fat concentration—up to acs staff like dissolves like, the nonpo- usually served. If you taste ice cream at room 50%—and supplies most lar sides of the proteins are temperature, it will taste overly sweet. You of the fat in ice cream. attracted to the nonpolar may have noticed this same effect with car- Premium ice creams fat globules. This is good bonated soft drinks. If consumed warm, they may have up to 20% in milk, but not so good

chemmatters | february/march 2014 7 in ice cream, in which the fat droplets should container. Both are derived from seaweed! Ice Cream coalesce to trap air. Without these stabilizers, ice cream might look like a . or False? So another emulsifier is added to allow ManyTrue myths and half-truths are float- Once you get all of the ingredients together the fat droplets to coalesce. This emulsifier ing around about ice cream. Test your in a mixture, you need to freeze the mixture replaces milk proteins on the surface of the ice cream knowledge by deciding to form ice cream. The dissolved solutes fat droplets, leading to a thinner membrane, whether each of the following is true (mostly sugar) in the liquid portion of the mix- which is more likely to coalesce during whip- or false: ping. A common emulsifier is lecithin, found ture lower its freezing point. A freezing point depression of 1.86 °C occurs for every mole in egg yolks. Lecithin is a generic term that 1. Margaret Thatcher, former prime refers to a group of molecules that consist of of solute added to 1 kilogram (kg) of water. In minister of the United Kingdom, helped long chains of fatty acids linked to a glycerol other words, if you dissolve one mole of sugar to develop the formula for soft-serve ice molecule, along with choline and a phosphate in 1 kg of water, water will no longer freeze at cream before she entered politics, while group (Fig. 2). 0 °C, but rather will freeze at –1.86 °C. working as a chemist in the food science industry.

O 2. Soft-serve ice cream was born on Memorial Day in 1934 H C -O -C -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2-CH2 -CH2-CH3 2 when an ice cream truck broke down, O and the salesman had to sell his melting ice cream, which was a big hit. H2C -O -C -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2-CH3 CH O 3 3. Modern-day ice cream was acciden- + H2C -O -P -O -CH2 -CH2 -N -CH3 tally discovered in 1782 by Martha O– CH Washington, wife of the 3 first U.S. president, who left a bowl of cream on the Figure 2. Chemical structure of a type of lecithin called phosphatidylcholine back steps of her home one night and, in the morning, found that it had Lecithin inserts itself between the fat glob- Freezing point depression is a colligative hardened into ice cream. ules, which helps the fat globules to stay property, meaning that the effect is observed together and, as a result, the air bubbles that regardless of the specific identity of the 4. The infamous Roman emperor are present in the mix are trapped by this solute—all that matters is how many Nero had slaves who would bring ice partially coalesced fat. This adds firmness and moles are dissolved. A typical batch of from the mountains so he could enjoy chilled desserts by pouring fruit juice texture to the ice cream, enabling it to retain ice cream will freeze at –3 °C (27 °F), due and honey over the ice. its shape. to the presence of all the dissolved solutes. Closely related to emulsifiers are stabiliz- 5. Ice cream were invented ers, which make the texture creamy. Stabiliz- in the late 1800s in New York to circum- ers have two roles: First, they prevent large vent a law prohibiting the serving of ice crystal formation. In the presence of stabiliz- cream on Sunday, hence the name. ers, ice cream contains small ice crystals, 6. Eskimo pies were originally called which melt more slowly than larger ice ! BrAiN FReEZe!! “I Scream Bars.” crystals, due to the insulating effect When ice cream touches of fats surrounding small crystals. the roof of your mouth, 7. Explorer Marco Polo was the first Second, emulsifiers act like a it may trigger a cold person to bring ice cream to the New sponge by absorbing, and headache. The World, bringing the recipe from China. cause is a dilation then locking into place, any of blood vessels liquid in the ice cream. 8. The was invented in your head in 1904, during the St. Louis Exposition Common stabilizers are located above in Missouri, when an ice cream vendor proteins, such as gelatin the roof of your ran out of bowls and substituted rolled and egg whites. Guar gum, mouth. When this nerve center gets up waffles instead. i locust bean gum, and k s l cold, it seems to ie s xanthan gum can also be ie 9. The was invented c e overreact and tries ik used. Look for carrageenan m to heat your brain. by the Earl of Sandwich in and sodium alginate on the England.

i st o c k. m , p h t s . sh u tte r k ingredients’ label of your ice cream

8 Chemmatters | February/march 2014 www.acs.org/chemmatters Ice Cream Types of ice cream generous helping of gummy bears! It contains or False? Soft-serve ice cream, , and less fat, but that means you can eat more True frozen yogurt. What is the difference? without feeling full. And to compensate for Regular ice cream is typically served at less fat, often a lot of sugar is added. The big- –12 °C, while soft-serve ice cream is served gest difference is that instead of cream, yogurt at –6 °C. This higher temperature is respon- is added as the primary dairy product. From sible for a softer product. Soft-serve ice there, the process is similar to making regular cream, or , for short, contains ice cream. less fat and more air than regular ice A recent trend is ice cream made with liq- cream. Soft serve with insufficient air uid nitrogen. One shop in San Francisco, will have a yellowish color. The whiter the soft serve, the better the quality. As tes y o f S m i tte n Ice Cr eam ice cream melts, you may have noticed this yellow color, which is simply the A dam L o we , c our actual color of the ingredients used to Ice cream shops serving desserts made with make it. By adding air and fluffing it up, liquid nitrogen are unique and very popular. ice cream is better able to reflect white light, producing the white color. This is because Calif., aptly named Smitten Ice Cream, has a the molecules in ice cream are large enough Look out for viewing area where customers can watch ice the weirdest to reflect visible light (whereas, for example, cream being made with liquid nitrogen, ice cream water molecules are too small to reflect visible accompanied by the impressive plume of fog light, because the size of a water molecule is flavor: garlic i that is released. Liquid nitrogen, which boils k flavor! s l smaller than the wavelengths of visible light). ie s at –196 °C, will freeze ice cream almost ie c e Frozen custard differs from ice cream in ik m instantly. Because the ice cream freezes so that it contains at least 1.4% egg yolks. Egg quickly, the size of the crystals is small, yolks are made of lecithin, an excellent emul- Answers to True or False resulting in a creamy texture. And because it sifier. The result is a product with a smoother, boils when it hits the mixture, the ice cream creamier texture. Another difference is that 1. Probably false. While Thatcher did work as a chemist for a company is aerated during the process. The popular frozen custard con- that developed soft-serve ice Dippin’ Dots are also made using liquid tains much less air cream, her actual role in develop- nitrogen. It is no exaggeration to say that ice than ice cream. No ing the product was likely minimal, cream made with liquid nitrogen is the cool- air is mixed dur- if at all. est ice cream around! ing its manufacture; 2. Likely true, but may not be the first. instead, air is introduced during mechanical agita- 3. False. Selected references tion as the frozen custard is Gooch, A. The Chemistry Behind Ice Cream. 4. Probably true. Chicago Tribune, June 30, 2004: http://articles. being made. It is churned more 5. Possibly true, but there are several chicagotribune.com/2004-06-30/entertain- ment/0406300068_1_ice-cream-homemade- slowly during its manufacture to minimize the other equally compelling stories ice-ice-crystals-form [accessed Dec 2013]. amount of introduced air. Less air leads to about to the origin of the . a thicker, denser product. Frozen custard is Halford, B. Ice Cream: The Finer Points of 6. Tr ue. Physical Chemistry and Flavor Release Make typically made fresh each day in the store. It this Favorite Treat so Sweet. Chemical & is frozen quickly to prevent large crystals—of 7. Story likely true, but may not be the Engineering News, Nov 28, 2004: http://pubs. water, lactose, or any added sugar—from first. acs.org/cen/whatstuff/stuff/8245icecream.html [accessed Dec 2013]. forming. 8. Story likely true, but may not be the Kilara, A.; Chandan, R. C.; Hui, Y. H. Ice Cream and Frozen yogurt is making a huge comeback first. Frozen Desserts. Handbook of Food Products these days, with self-serve frozen yogurt Manufacturing, John Wiley Online Library, 9. False. Don’t mistake the ice cream Chapter 74, pp 593–633, Aug 1, 2006: http:// shops offering a plethora sandwich for the actual sandwich, www.researchgate.net/publication/227580162_ of toppings popping up which was invented by the Earl of Ice_Cream_and_Frozen_Desserts/file/ seemingly on every Sandwich. 9c9605151b162a696c.pdf [accessed Dec 2013]. corner. Frozen yogurt Note: If you are concerned about the is viewed as a healthier Brian Rohrig teaches chemistry at Metro Early ambiguity of these answers, now you College High School in Columbus, Ohio. His most alternative to ice cream, know why ice cream historians are still recent ChemMatters article, “Hot Peppers: Muy

i st o c k. m , p h t s . sh u tte r k unless you top it off with a arguing about the origins of ice cream! Caliente!” appeared in the December 2013 issue.

chemmatters | february/march 2014 9 How to Make Ice Cream in a Bag A Delicious Experiment With Freezing Point Depression

By Anne Marie Helmenstine, Ph.D. Updated November 28, 2019

You can make ice cream in a plastic bag as a fun science project. The best part is you don't need an or even a freezer. This is a fun and tasty food science project that explores freezing point depression.

Materials

1/4 cup sugar 1/2 cup milk 1/2 cup whipping cream (heavy cream) 1/4 teaspoon vanilla or vanilla flavoring (vanillin) 1 (quart) zipper-top baggie 1 (gallon) zipper-top baggie 2 cups ice Thermometer 1/2 to 3/4 cup sodium chloride (NaCl) as table salt or rock salt Measuring cups and spoons Cups and spoons for eating your treat

Procedure

1. Add 1/4 cup sugar, 1/2 cup milk, 1/2 cup whipping cream, and 1/4 teaspoon vanilla to the quart zipper bag. Seal the bag securely. 2. Put 2 cups of ice into the gallon plastic bag.

https://www.thoughtco.com/how-to-make-ice-cream-in-a-bag-602195 3. Use a thermometer to measure and record the temperature of the ice in the gallon bag. (Optional) 4. Add 1/2 to 3/4 cup salt (sodium chloride) to the bag of ice.

5. Place the sealed quart bag inside the gallon bag of ice and salt. Seal the gallon bag securely.

6. Gently rock the gallon bag from side to side. It's best to hold it by the top seal or to have gloves or a cloth between the bag and your hands because the bag will be cold enough to damage your skin.

7. Continue to rock the bag for 10-15 minutes or until the contents of the quart bag have solidified into ice cream.

8. Open the gallon bag and use the thermometer to measure and record the temperature of the ice/salt mixture. (Optional) 9. Remove the quart bag, open it, serve the contents into cups with spoons.

How It Works

Ice has to absorb energy to melt, changing the phase of water from a solid to a liquid. When you use ice to cool the ingredients for ice cream, the energy is absorbed from the ingredients and from the outside environment (like your hands, if you are holding the baggie of ice.)

When you add salt, it lowers the freezing point of the ice, so even more energy has to be absorbed from the environment for the ice to melt. This makes the ice colder than it was before, which is how your ice cream freezes.

Ideally, you would make your ice cream using "ice cream salt," which is just salt sold as large crystals instead of the small crystals in table salt. The larger crystals take more time to dissolve in the water around the ice, which allows for more even cooling of the ice cream.

Other Types of Salt

You could use other types of salt instead of sodium chloride, but you couldn't substitute sugar for the salt because (a) sugar doesn't dissolve well in cold water and (b) sugar doesn't dissolve into multiple particles, like an ionic material such as salt.

Compounds that break into two pieces upon dissolving, like NaCl breaks into Na+ and Cl-, are better at lowering the freezing point than substances that don't separate into particles because the added particles disrupt the ability of the water to form crystalline ice.

The more particles there are, the greater the disruption and the greater the impact on particle- dependent properties (colligative properties) like freezing point depression, boiling point elevation, and osmotic pressure. https://www.thoughtco.com/how-to-make-ice-cream-in-a-bag-602195 The salt causes the ice to absorb more energy from the environment (becoming colder), so although it lowers the point at which water will re-freeze into ice, you can't add salt to very cold ice and expect it to freeze your ice cream or de-ice a snowy sidewalk. (Water has to be present.) This is why NaCl isn't used to de-ice sidewalks in areas that are very cold.

Questions:

1. What observations did you make during the process of ice cream making?

2. What are some of the scientific principles at work while you made your ice cream?

3. How did your ice cream taste?

4. If you were to make more ice cream, what changes to the process might you make? Why?

5. If you were to make more ice cream, what changes to the ingredients might you make? Why?

https://www.thoughtco.com/how-to-make-ice-cream-in-a-bag-602195 Inventing a longer-lasting popsicle By Emily Matchar, Smithsonian.com on 09.10.18 Word Count 796 Level MAX

Can a popsicle be made to last longer before it turns into a melty mess? A British design firm says yes. Photo by: iStock/Getty Images

There's less than a month to go until the official start of fall, and it's hot. Hot, hot, hot. As a heat wave rolls eastward from Chicago, 17 states are under heat advisories. The expected high today in Washington, D.C., is 94 degrees. In New York it's 95. Dallas is slated to hit 97.

Sounds like time for a popsicle. But you better eat it indoors, lest you wind up with more of it melted down your sleeve than in your mouth.

Or you could try this: the world's first non-melting "ice lolly" (British for "popsicle"), invented by the United Kingdom food-focused design firm Bompas & Parr.

"This has taken over a year to perfect and has involved speaking to a whole host of experts from physicists to chemists," says Sam Bompas, the firm's co-founder. "While the physicists' suggestions were mostly theoretical, some of the chemists' were far from food safe! Balancing your ingredients is even more crucial than in a regular recipe so you can hit the bliss point of flavor, savor and texture."

This article is available at 5 reading levels at https://newsela.com. The key to the popsicles' heat tolerance is strands of fruit fibers embedded within the pop. The fibers lower the pops' thermal conductivity, making them melt more slowly than ordinary frozen treats. Bompas & Parr say the prototype pops last "hours longer" than regular popsicles under the same temperature.

The popsicles were inspired by pykrete, a frozen composite material made from sawdust and wood pulp dispersed in ice. The substance, created by 20th-century British inventor Geoffrey Pyke, is much stronger than regular ice and melts much more slowly. Pyke envisioned pykrete as a perfect material for building gigantic floating aircraft carriers during World War II. It would save on steel, he said, which was already in high demand due to the war, and could be made more cheaply as well. Winston Churchill was on board, and the building of a secret model pykrete aircraft carrier commenced on a lake in Alberta, Canada, with the code name Project Habakkuk. The project went beyond budget and was eventually shut down.

Pykrete lived on, though mostly as a curiosity, occasionally popping up in futurism expos or on shows like "MythBusters" (they used it to build a boat; it fell apart in less than half an hour).

Pykrete is far from the only fascinating story in the history of frozen treats. The history of ice cream is a tale of creativity and innovation. Some the most interesting parts are tied to wartime. During World War II, some fighter pilots fought boredom and low morale by pouring ice cream ingredients into their planes' ammo carriers and ascending to high altitudes to freeze the mixture. As the substance was initially too icy, they rigged small propellers to the ammo buckets to churn the ice cream as it flew. The name of the project? Operation Freeze. Then, in 1945, the U.S. Navy spent $1 million turning a concrete barge into a "floating ." The sweet ship sailed around the Pacific supplying sailors with their favorite treat. Later, during the Korean War, the Pentagon made an official statement insisting soldiers got ice cream at least three times a week.

Bompas & Parr is unveiling their non-melting popsicles at "SCOOP: A Wonderful Ice Cream World," an exhibit of the British Museum of Food, itself a creation of the firm. The exhibit showcases the science and history of ice cream and other frozen desserts. Visitors can walk through a scent "cloud," stand in a subzero chamber, view a vast collection of ice cream paraphernalia, and learn about the bloody 1980s Ice Cream Wars, when rival gangs sold drugs and other contraband from ice cream vans. They'll also have the chance to taste historically inspired flavors like cucumber and candied fruit, as well as experience ice creams of the future, with fizzy and glow-in-the-dark versions. A special feature will look at the life of Agnes Marshall, the 19th-century British "Queen of Ices," who patented an improved ice cream machine in 1885 and suggested using liquid nitrogen for ice cream more than a century before the technique was de rigueur in molecular gastronomy restaurants.

This is just the latest food science creation from Bompas & Parr, known for their whimsical, highly Instagrammable food spectacles, from gelatin molds of architectural wonders to flavored fireworks.

Though the non-melting pops can be made in any flavor, Bompas & Parr will be demoing an apple variety at the exhibit. If the prototypes are a success with visitors, the firm hopes to manufacture them for distribution in supermarkets.

This article is available at 5 reading levels at https://newsela.com. The popsicles taste more or less like ordinary pops, Bompas says, though, due to the fiber content, "you could describe them as a tad more chewy."

Writing Prompt: How did Bompas and Parr create a popsicle that takes longer to melt? What aspects of science were studied or used to create this popsicle? Where did they originally get the idea from? Do you think this idea would work for ice cream? Explain

This article is available at 5 reading levels at https://newsela.com.