ChemShorts for Kids  —  2014
Copyright 2014 by the Chicago Section of the American Chemical Society

by Kathleen Carrado Gregar, PhD, Argonne National Labs
kcarrado@anl.gov

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.


January 2014

Be An Amateur Antiques Detective!

Kids, do you like using a black light to check for glowing objects? Do you like to solve clues and riddles? Are you curious about how things are made? If you answered yes to all of these questions then you might like this activity. Some antiques, collectibles and memorabilia have value if they're authentic and in good shape. Many people like to go to garage sales, antique shows, or even just "picking", to find interesting and valuable items.

It's often very hard to tell if an old object is authentic or fake, or if it's been repaired or touched up. But using a black light can offer some clues. That's because some telltale signs of repair and signs of age will fluoresce under ultraviolet light.

"Black light" is another name for ultraviolet light, that is, light that is of such a short wavelength that it is beyond the violet end of the visible part of the spectrum. As such, our eyes can not see this light or most objects illuminated by this wavelength of light, so it looks "black" to us.   However, a number of materials fluoresce when illuminated by this light. That is to say, they absorb light energy in this region of the spectrum, and re-emit the energy at a longer wavelength, which is visible to the human eye.  DayGlo® highlighter pens make use of this property by containing dyes that convert the ultraviolet component of sunlight or of some interior lamps to light of the same color as the pen color, to make the pen markings appear extra bright.   We will use this ability of some materials to fluoresce when exposed to ultraviolet light to perform our detective work in this month's experiments.

  1. Detect Ceramic Repairs. Check an old-looking plate, teacup, or figurine in a darkened room. Use a handheld black light to check for repairs. If glue was used to repair cracks or replace chips then it will be obvious under the black light. This is because modern glues fluoresce under ultraviolet light. Modern paints also fluoresce, so you can also see touch-ups and repainting jobs.
  2. Confirming Age of Paper Items. Old postcards, books, signs, photos, posters etc. made before the late 1930's rarely glow under a black light. But the bleaches and dyes used in modern papers fluoresce strongly. Knowing this can help you detect a forgery or a fake.
  3. Dating Cloth Items. Cloth items include clothing, stuffed animals, rag dolls, and quilts. Many modern cloth fibers, including sewing thread, are made of polymers like rayon and polyester. These glow under a black light. Items that don't glow might be old and antiques. However, even if they're old, they might glow if they've been washed. That's because modern laundry detergents have additives that glow. So these items need extra testing.

Check items around your home to see what you can deduce about their ages!

NOTE: Standard safety precautions apply -- do not look directly at the black light.

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References:

About.com Antiques "Ways to Test Antiques & Collectibles with a Black Light" by Pamela Wiggins
http://antiques.about.com/od/resourcesforbeginners/tp/aa122205.htm

February 2014

Blow Frozen Bubbles

Kids, there are some incredible frozen bubble photos on-line that are amazing. You too can blow bubbles that freeze into delicate frost patterns. You can even pick up the bubbles and examine them before they pop. All you need is bubble solution, a bubble wand, and a cold winter day (below freezing, at least).

It helps if you blow the bubbles close to a cold surface, so they don't freeze in the air and break upon landing. You can catch bubbles on mittens/gloves or on snow or ice. You should see a frost pattern forms on the bubble surface. The bubbles will eventually pop, but with a bit of practice you should be able to pick them up and examine them first.

The frost creates magical patterns in the freezing bubbles. The smaller ones may freeze momentarily in mid-air, and then fall down and scatter like thin glass chips. The bigger ones should freeze more slowly on the surface.  Photographer Angela Kelly noted "...how they would freeze completely before the sun rose but that once the sun was in view they would defrost along the tops or cease freezing altogether.  We also noted how they would begin to deflate and implode in on themselves making them look like alien shapes or in some cases shatter completely leaving them to look like a cracked egg.”

Any bubble solution will work. You can make your own detergent and water solution or make stronger bubbles using glycerin or corn syrup.  See the June 2013 issue of ChemShorts for Kids for the best recipes.  If you don't have seriously cold winter, your other option is to blow bubbles over dry ice (see below for a link with directions on how to do this).

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References:

Angela Kelly, http://www.boredpanda.com/frozen-bubbles-winter-photography-angela-kelly/
Anne Marie Helmenstine, About.com Chemistry, http://chemistry.about.com/od/bubbles/fl/Frozen-Bubbles-Blow-Bubbles-in-Winter.htm
ChemShorts June 2013 bubble recipes:  http://chicagoacs.net/ChmShort/CS13.html
Make frozen bubbles using dry ice:  http://chemistry.about.com/cs/howtos/a/aa012004.htm


March 2014

Make a Color Wheel from Milk

Kids, if you just add food coloring to milk, not a whole lot happens. However, it only takes one simple ingredient to turn the milk into a swirling color wheel. Here is what you do.

Materials:

Instructions:

How It Works:

Milk consists of a lot of different types of molecules, including fat, protein, sugars, vitamins, and minerals. If you had just touched a clean cotton swab to the milk (try it!), not much would have happened. The cotton is an absorbent, so you would have created a current in the milk, but you wouldn't have seen anything especially dramatic happen.


When you introduce detergent to the milk, several things happen at once. The detergent lowers the surface tension of the liquid so that the food coloring is free to flow throughout the milk. The detergent reacts with the protein in the milk, altering the shape of those molecules and setting them in motion. There is also a reaction between the detergent and the fat in the milk. This, by the way, is how detergent helps lift grease off dirty dishes. During the reaction, the colorful molecules in the food coloring get pushed around. Eventually equilibrium is reached, but the swirling of the colors continues for a while before stopping.

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References:
Anne Marie Helmenstine, About.com Chemistry, 
http://chemistry.about.com/od/chemistryhowtoguide/a/magicmilk.htm
http://www.youtube.com/watch?v=lf4HHazghGs


April 2014

Regular Salt to Rock Salt

Kids, have you ever seen a chef cook with pink salt or put their food on a big pink slab that looks like a large marble cutting board?  Rock salt is a natural, unrefined salt consisting of large crystals containing mineral impurities. Sometimes the impurities give color to the salt.  Therefore, natural salt can be white, pink, red, or even black. The grain size, color, and flavor make rock salt popular for recipes, bath products, and crafts, but it can be very expensive. You can make your own rock salt from regular table salt.

You'll need:

Process:

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References:
http://chemistry.about.com/od/crystalrecipes/fl/How-To-Make-Rock-Salt.htm?nl=1


May 2014

Honeycomb Candy - Cooking with CO2

Kids, honeycomb candy is easy to make and has an interesting texture that is caused by carbon dioxide bubbles trapped inside of it. The carbon dioxide is produced when baking soda (sodium bicarbonate) is added to a hot simple syrup. The bubbles in the candy make it light and give it a honeycomb appearance.

Materials:

Directions:

The creation of carbon dioxide (CO2) gas in the candy is the same process that's used in making some baked goods.  In this case the candy forms a hard shell around the bubbles.

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References:   By Anne Marie Helmenstine, Ph.D.
http://chemistry.about.com/od/foodscienceprojects/a/honeycombcandy.htm
http://www.honeybeesuite.com/how-acid-is-honey/


June 2014

Kool-Aid® Powder Chemistry

Kids, can you make a fizzy reaction without using vinegar?  Yes you can!  There are many experiments where the trick is to mix baking soda with vinegar, creating carbon dioxide fizzy gas and water.  But if you don't happen to have vinegar around, here is another way to, for example, make that science fair volcano work.

All you need are some Kool-Aid packets in a variety of colors (the kind you have to add sugar to drink), baking soda, a cookie sheet or shallow plastic tray, and either a small bowl of water with some medicine droppers, or a spray bottle with water (not vinegar!).  This is a very inexpensive experiment and is fun for kids of all ages.

Sprinkle the Kool-Aid powder onto a cookie sheet. You can add different flavors in separate lines or mix them all over the sheet at your preference. Cover most of the Kool-Aid with a very thin layer of baking soda. Leave one line (or one area) of the Kool-Aid plain, without the baking soda.  You could use a mesh strainer over the tray and to sprinkle the baking soda evenly. Add water first to the plain Kool-Aid.  What happens?  

Then add water to the baking-soda-covered Kool-Aid.  What happens?   The citric acid in the Kool-Aid powder reacts with baking soda (a base) when you add water.  They do not react with water individually, but they react with each other when dissolved in water.  When they react with each other they form sodium citrate, carbon dioxide and water. The end result is wonderful smelling, vibrantly colored bubbles!

This activity can get pretty messy, obviously. You should be in play clothes and if you’re doing this activity inside, cover your floor with a splat mat, towel, cheap plastic tablecloth, etc. Some people prefer these fun, bubbly experiments over the traditional baking soda and vinegar activities because the Kool-Aid smells so much better than the vinegar.

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References:
http://lifeispeachyblog.com/surprise-color-eruptions-without-vinegar/
http://mommasfunworld.blogspot.com/2013/02/dancing-powder-kid-science.html


September 2014

Ice Art

Kids, make a colorful ice sculpture while learning about freezing point depression. All you need is ice, salt, and food coloring!   You can use any type of salt.  Coarse versions like rock salt or sea salt work great, as does the finer-grained table salt (all of these are sodium chloride, NaCl).  You can even use other salt compositions like Epsom salts (magnesium sulfate, MgSO4).   For colors use water-based paints such as watercolors or tempera paints, or food coloring.

What To Do

  1. Make ice. You can use ice cubes but larger pieces of ice are best. Freeze water in shallow plastic, disposable storage containers. Fill them only part way to make relatively thin pieces of ice. This is because the salt can melt holes all the way through thin pieces, making interesting ice tunnels.
  2. When you’re ready, remove the blocks of ice from the freezer and place them on a cookie sheet or in a shallow pan. If the ice doesn't come out easily, run warm water around the bottom of the container.
  3. Sprinkle salt onto the ice or make little salt piles on top of the pieces. Experiment!
  4. Dot the surface with coloring. The coloring doesn't color the frozen ice, but it follows the melting pattern. You'll be able to see channels, holes, and tunnels in the ice, plus it looks like art work.
  5. You can add more salt and coloring, or not. Explore however you like.
  6. NOTE! This is a messy project. You can perform it outdoors or in a kitchen or bathroom. The coloring will stain hands and clothes and surfaces.

How It Works

The salt lowers the freezing point of water through a process called freezing point depression. The ice starts to melt, making liquid water. Salt dissolves in the water, adding ions that decrease the temperature at which the water could re-freeze. As the ice melts, energy is drawn from the water, making it colder. Salt is used in ice cream makers for this reason. It makes the ice cream cold enough to freeze. Did you notice how the water feels colder than the ice cube? The ice exposed to the salty water melts faster than other ice, so holes and channels form.

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References:
http://chemistry.about.com/od/chemistryactivities/a/Melting-Ice-Science-Experiment.htm


October 2014

Powdered Olive Oil

Kids, what is molecular gastronomy?  It's food science that seeks to understand the chemical and physical transformations that occur during cooking.  It uses chemistry to put a modern spin on traditional foods. In this experiment, you will combine maltodextrin powder with olive oil to make a powdered oil.  Maltodextrin is a carbohydrate powder derived from starch that dissolves the instant it hits your mouth.  It melts away with no gritty or powdery sensation, so you taste the oil. You will need maltodextrin and olive oil.  Food-grade maltodextrin is sold under many names, including N-Zorbit M, Tapioca Maltodextrin, Maltosec, and Malto.  Maltodextrin is derived from a number of sources, and, depending on your source, you may get different results.  Most of these references recommend a tapioca-based maltodextrin.

Whisk together maltodextrin and oil or combine them in a food processor. You can use a fork or spoon, if you don't have a whisk. Use about half and half oil and maltodextrin by weight for your first experiment.  If the resulting mixture is too oily, add more maltodextrin; if too dry, more oil.  For a fine powder, you can use a sifter or push the powder through a strainer. You can serve the powdered olive oil by itself in a decorative spoon or as a topping on dry foods, such as crackers.

An alternative method is to combine maltodextrin with other fatty products such as peanut butter. The only 'rule' is to mix it with a lipid (a fat-based material), not water or a high-moisture ingredient.

Note: Don't put the powder in contact with a water-based liquid because it will dissolve. The powder will last for a day at room temperature or for several days if sealed and refrigerated. Be sure to keep the powder away from moisture or a high-humidity environment.

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References:
http://chemistry.about.com/od/ediblescienceprojects/fl/How-To-Make-Powdered-Olive-Oil-Molecular-Gastronomy.htm
http://www.molecularrecipes.com/transformation/olive-oil-powder/
http://www.molecularrecipes.com/techniques/converting-high-fat-liquids-powder/
http://www.seriouseats.com/recipes/2011/09/olive-oil-powder-maltodextrin-modernist-cuisine-recipe.html
A couple of videos of the process:
https://www.youtube.com/watch?v=BVsGepp2Id0 
https://www.youtube.com/watch?v=V9KD4fnSF3s


November 2014

Homemade Vinegar

Kids, what is vinegar? Vinegar is a product of the fermentation of alcohol by bacteria to for the purpose of producing acetic acid.  Acetic acid has a tangy taste and it is also useful for household cleaning. Vinegar can be produced slowly from fruit juice or fermented juice. It can be produced quickly by using a culture called Mother of Vinegar which is a slimy, harmless substance of acetic acid bacteria (Mycoderma aceti) and cellulose.

Slow Method (Requires 3 weeks to 6 months)

Start with apple cider or fermented fruit juice that contains 0-10% real fruit juice and no added sugar. Either fresh or hard cider will work. Fresh cider takes a few weeks to convert to vinegar because it first ferments into hard cider before becoming vinegar.

Pour the starting liquid into a dark bottle. Fermentation occurs in the dark so you either need a dark container or you need to keep the liquid in a dark place. A clear bottle lets you see what is happening but you need to keep it in the dark the rest of the time. The fermentation process requires air. Cover the mouth of the bottle with a few layers of cheesecloth and secure them with a rubber band, so you don't get insects or dust into your recipe.

Place the container in a dark, warm place at 60-80°F (15-27°C). Fermentation occurs more quickly at a warmer temperature. Initially the bacteria will cloud the liquid, eventually forming a gelatinous layer on the top of the starting material.

Avoid disturbing or stirring the mixture. After 3-4 weeks, smell the covered bottle. Unwrap the cheesecloth if it smells like strong vinegar and then draw off a little liquid, and taste it. Go to the next step if the vinegar passes the taste test. Replace the cheesecloth if you don't like the taste and allow the solution to sit longer. Note: a bottle with a spigot at the bottom makes the taste test much easier, since you can remove a little liquid without disturbing the Mother of Vinegar forming at the top of the container.

Filter the liquid by pouring it through a coffee filter or cheesecloth. The slimy material on the filter is called Mother of Vinegar and can be used to speed the production of future batches. The liquid is the vinegar. Have an adult partner boil the vinegar at 170°F for 10 minutes to kill any undesirable microorganisms and remove residual alcohol (this is called pasteurization). Unpasteurized vinegar is safe but it will have a shorter shelf life (4-6 weeks) and needs to be refrigerated. Pasteurized vinegar may be stored in sealed, sterilized containers for several months at room temperature.

Fast Method (Requires days to weeks)

Add some Mother of Vinegar to the bottle containing the fermented liquid and proceed as before. You can buy unfiltered cider vinegar that contains Mother of Vinegar. Any vinegar you make will contain Mother of Vinegar and can be used to produce subsequent batches of vinegar more quickly.

Reference: Anne Marie Helmenstine at Chemistry.About.com
http://chemistry.about.com/od/foodscienceprojects/a/How-To-Make-Homemade-Vinegar.htm?nl=1


December 2014

Poinsettia pH Paper


Kids, here's a way to use holiday plants for science! Many plants contain pigments that are responsive to changes in acidity. An example is the poinsettia plant, which has colored leaves called bracts (they aren't really flowers). You can extract the red pigment from bright-red colored poinsettias and use it to make your own pH paper strips to test whether a liquid is an acid or a base. 

Chemists use a pH scale to measure the extent to which a solution is an acid or a base.  The smaller the number on the pH scale, the more acid is the solution, and similarly, a liquid that measures high on the pH scale is considered basic.  Neutral solutions, such as tap water, measure close to 7 on the pH scale, while acids typically measure between 1 (very acid) and 6, while a solution measuring between 8 and 14 are basic, with a number above ten is very basic, such as a solution of lye or caustic soda.

Materials

Procedure

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References:

YouTube Video of the process:   http://www.youtube.com/watch?v=dYOcCJPcXyM

Anne Marie Helmenstine, PhD: http://chemistry.about.com/od/chemistryblogs/a/poinsettia.htm

 

 

Updated  11/6/14