by Dr. Kathleen A. Carrado, Argonne National Labs |
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
Kids, we all know that aspirin is a medicine, but did you know that it is also a chemical? It’s name is acetylsalicylic acid. You have probably heard that it can cause stomach discomfort in some people – maybe even yours, too. One way to lessen this is to combine the aspirin with an acid buffer — a combination of chemicals that reduces acidity. This buffered aspirin is a genuine help for this group of people. But for people who have take aspirin every day (like arthritis sufferers), this is not good enough. For them, chemists invented specially coated aspirin tablets that pass through the stomach without dissolving. The coating resists the acid juices of the stomach, but dissolves quickly in the basic environment of the small intestine. Called “enteric” aspirin, they obviously take a bit longer to work.
In this column you will simulate a stomach to observe the chemistry of aspirin there. You can see the difference between regular aspirin, buffered aspirin, and enteric aspirin by testing the tablets in neutral, acidic, and basic solutions. Your stomach is acidic, but your small intestine is basic. Begin with three clear glasses or plastic cups. Add 1/2 cup (120 ml) of water to each container. Note the time, then simultaneously add a regular aspirin tablet to one container, a buffered aspirin to another, and an enteric aspirin tablet to the third. Note changes in the tablets at 30-second intervals until no further change is evident. To simulate the acid environment of the stomach, repeat this procedure using vinegar in each container instead of water. You will see one of the tablets dissolve more vigorously than before. To simulate the basic intestine, repeat the experiment once more using a solution made by adding 16.3 g (1.5 teaspoons) of powdered baking soda, NaHCO3, to each 1/2 cup of water. One of the tablets will dissolve suddenly after a delay of 20-30 minutes.
For the more technical students in the audience, we did a bit of research into buffering agents and coatings. The typical buffers used to raise the pH of aspirin are MgO and CaCO3 (magnesium oxide and calcium carbonate). Enteric coatings appear to have recently changed to an aqueous acrylic resin such as methacrylic acid copolymer, although phthalates of cellulose polymers may still be used.
Here is another interesting aspirin chemistry note. As acetylsalicylic acid ages, it can decompose to salicylic acid and acetic acid. If you have a very old bottle of asprin around the house, open it and take a whiff. It might smell like vinegar, which is dilute acetic acid. This is one reason why there are expiration dates!Gail Marsella and David Robson, ACS ChemMatters, February 1993.
http://antoine.frostburg.edu/chem/senese/101/acidbase/faq/buffered-aspirin.shtml
Enteric coatings: Pharmaceutical Technology, 2004Kids, want to do an experiment than can be considered as more on the icky side? While “Glitter Slime” doesn’t sound so bad, we are going to use it as a model for trapping allergens. One way that our noses keep allergens like pollen, spores and dust from our lungs is to use a sticky, slimy material called mucus. Breathe air containing these particles through your nose and it gets stuck in the mucus, becoming safely trapped. This helps us from getting sick. The glitter in the slime will imitate this trapping. We have discussed making slime by various methods in this column before (5/94, 12/94), but we’ll repeat one of them here with some important modifications.
Pour 2 tsp water and 1 tsp clear gel glue into a small ziplock bag. Seal the bag and squeeze the bag with your fingers until the contents are thoroughly mixed. Now make a borax solution as follows. Pour ¼ cup of water into a plastic cup. Add ½ tsp borax to the water and stir with a plastic spoon until dissolved. Add two drops of food coloring and stir that in. Add 1 tsp of the borax solution to the glue in the ziplock bag. Seal and mix again. Now you can open the bag and remove the slime. How does it feel? Put the slime back in the bag and add ¼ tsp glitter. Seal and mix. Open the bag and observe the contents. Does the glitter stick to the slime? You can use glitter gel glue if desired, although the concept of the glitter sticking to the slime like dust in mucus is somewhat lost. You can also use 1 tablespoon small Styrofoam craft beads in clear gel glue instead of glitter. The beads versus the glitter not only feel different, but they can also represent the different sizes of spores versus dust, for example.
So what is the chemistry here? The glue-water mixture has very long chains of molecules linked together called polymers. In this case they are called polyvinyl acetate. When borax is added, the chains link together and a slimy glob forms. Glitter is not easily removed from the sticky substance. The slime represents mucus that is in our bodies. Natural mucus contains sugars and proteins, which are also long-chain molecules. Mucus is not only in our noses; it also coats the insides of our stomachs. Without a protective coating of mucus there, the powerful acids used to digest our food would also digest the stomach!
As for cleanup, pour borax down the drain and throw everything else away in
the trash, including the slime. Your slime can be stored in an airtight
container for a few days to prevent it from hardening. (And, in case you need
to know, hardened slime can be washed out of clothing with warm soapy water).
-------------
References: ACS National Chemistry Week 2004 “Celebrating Health & Wellness”, Celebrating
Chemistry NCW 2004 newspaper, page 8.
Facilitator tips found on: www.chemistry.org/portal/resources/ACS/ACSContent/ncw/PDF/ncw_04_facilitatortips.pdf
Kids, “bath bubblers” or “bath bombs” are fancy bath bars that can be found at bath & body stores. But even better, they are easy to make with materials found in the home. A chemical reaction occurs when a bath bubbler comes in contact with water which involves citric acid (H3C6H5O7, a weak acid) and baking soda (NaHCO3 , a weak base).
You will need baking soda, cornstarch (C6H10O5), citric acid, Epsom salts (MgSO4-7H2O), sweet almond oil, witch hazel, a fragrance oil, food coloring, molds (three small plastic Easter eggs, small muffin tins or ice cube trays), aluminum foil, plastic wrap, and rubber gloves. Measure these dry ingredients into a large bowl: 1/2 cup baking soda, 1/4 cup cornstarch, 1/4 cup citric acid, and 2-1/2 Tbsp Epsom salts. Grind the lumps out with a large plastic spoon and mix well. Measure and combine these liquid ingredients into a small cup: 4 tsp almond oil, 3/8 tsp witch hazel, 1/8 tsp of fragrance oil, and 1 drop of food coloring. Seal plastic wrap over the cup. While holding the wrap in place over the top of the cup, swirl the ingredients to mix them well.
The next step is for an adult partner. While stirring constantly with gloved hands, have them slowly add the liquid mixture to the dry mixture in the bowl. (If too much liquid hits the dry ingredients a reaction will start, so go slowly; using witch hazel instead of water helps). Mix in all of the liquid. The mixture should be crumbly (like damp sand). Now you can pack the damp mixture into molds. Press firmly. Work quickly so that it does not dry out completely. (When using egg molds, pack each side and then add some loose mixture to one half and firmly push the halves together. Do not twist, and the halves do not need to fit together perfectly). Let the molds rest undisturbed for 48 hours. Unmold the bubblers onto aluminum foil, tapping gently against the tabletop. Without twisting, unmold one side at a time.
Try two bubblers by placing one in a container of hot water and another in cold water. Record your observations about the fizzing. Can you guess what gas is causing the bubbles in this reaction? Store the rest of the bubblers for yourself in a sealed container (most plastic wraps will let humidity in).
Why is water needed to start the reaction? Water dissolves the solids and enables the ions to move, collide, and produce a reaction in solution. The reaction is citric acid with baking soda to produce carbon dioxide. Carbon dioxide fizzes and the bubbler releases the fragrant oils into the bath water as it whirls and spins. How does the water temperature affect the action? Bath bubblers will spin and fizz in water. The rate of bubbling increases with an increase in water temperature. Why could humidity lead to problems? If high enough, humidity can provide enough moisture to dissolve the solids and start the bubbler reaction.
Notes: Sweet almond oil and citric acid can be found in
natural food stores; fragrance oils are in craft stores that sell soapmaking
supplies. Soap molds from craft stores can be used for fancier shapes. Do not
substitute ascorbic acid for citric acid because it yellows and freckles the
bar.
-------------
References: Journal of Chemical Education, 2003, 80(12),
1416A by Mary E. Harris and Barbara Walker;
Brenda
Sharpe at http://www.ncf.carleton.ca/~aj471/BathBombs.html
Kids, everyone knows that a day or two after you blow up a balloon it gets smaller. This is because some of the air leaks out through microscopically small holes in the balloon’s wall. In this activity, you will test how the molecules that we can smell from a flavoring extract can move through the rubber wall of a balloon and into our noses.
You will need 3 rubber balloons, a permanent marking pen, 3 disposable 3 oz plastic cups, 3 droppers, and 3 different flavoring extracts (vanilla, peppermint, and orange extracts work well). Here is what you do. Use the marking pen to write #1, #2, and #3 on each of your balloons. Do the same with the three plastic cups, and place a dropper in each one. Have an adult partner pour a small amount of a different flavoring extract into each of the cups, but don’t let them tell you which is which. It will be up to you to guess which extract is in which balloon. Use the dropper to place 10 drops of the extract in cup #1 into balloon #1. Be sure to place the tip of the dropper as far into the balloon as possible before squeezing the dropper bulb so the extract does not get into the neck of the balloon. Be careful not to get the extract on your hands, or you will end up smelling your hands instead of what is inside the balloon. Repeat for extracts #2 and #3.
After making sure that there is no extract solution on the lip or neck of the balloon, blow them up, tie off the necks, and shake them a few times. Blow each balloon up to about the same size. Try to smell the extract inside balloon #1 by holding the balloon about 30 cm (1 foot) in front of your face in one hand, and using your other hand to fan the air around the balloon towards you. Slowly move the balloon towards your nose until you begin to smell the extract. Repeat for balloons #2 and #3. Confirm with your adult partner that your guesses are correct. For clean-up, hold each balloon over a sink, have the adult partner cut the knot off of the balloon and drain its contents. Pour any excess extracts down the drain, throw away the deflated balloons and any trash, and wash your hands.
Try these variations. Compare natural and artificial vanilla flavorings to see if you can tell a difference. Try inserting cloves or pieces of garlic, nutmeg or onion inside of balloons to see if their scents will pass through the rubber membrane of the balloon. Try substituting snack-size zip-closing plastic bags for the balloons. So, where is the chemistry here? To our eyes, the rubber membrane making up the wall of the balloon looks solid, without any holes. Yet somehow the extracts make it out of the balloons and to your nose. There are actually millions of holes, of course, but they are very, very tiny. Air molecules and most scent molecules are small enough to fit through these holes.
-------------
Reference: Celebrating Chemistry NCW 2004 newspaper, page 8. Facilitator tips found on:
www.chemistry.org/portal/resources/ACS/ACSContent/ncw/PDF/ncw_04_facilitatortips.pdf
Kids, is there an easy way to compare the sizes of gas molecules? Yes there is, and all you need are two regular balloons and some helium. Have one of the balloons inflated with helium (you can go to a store and ask them to inflate a regular balloon for you). Then inflate the second balloon with air. Try to make the second balloon as identical to the first balloon as possible in size and shape. Leave the balloons next to each other for a couple of days. Observe and compare the size of each balloon as time goes by. What happens?
Even though a balloon may look like it has a solid surface, it really has very small holes in it. These pores, as small as they may be, are big enough to allow gas molecules out. In this experiment, we had two balloons with two different types of gases in them: air and helium. Air is mostly oxygen and nitrogen. Since the helium balloon deflated faster (it should have, anyway!), the helium gas molecules must have been smaller than either the nitrogen or the oxygen molecules. Therefore, we can use a balloon to compare the sizes of gas molecules.
Nitrogen and oxygen are in a group of gases that are called “diatomic”. This means that their molecules exist only in pairs. You don’t find, for example, oxygen by itself as O in nature. Instead, you find O2. Helium, however, is not part of this group and exists purely as He. In terms of atomic size, O and He are fairly similar. But in terms of molecular size, O2 and He are different enough to measure just by using the balloon test. Since nitrogen and oxygen are bigger than helium, they have less chance of escaping through pores such as those found in the balloons. Therefore, the balloon inflated with air should deflate more slowly than the one with helium.
Other diatomic gases include hydrogen (H2), fluorine (F2), nitrogen (N2), and chlorine (Cl2). In addition, bromine (Br2), a liquid, and iodine (I2), a solid, also appear in pairs. Try to devise your own acronym to help memorize these special elements based on their chemical symbols (like HOFBrINCl?).
Note: don’t use Mylar balloons; that’s a different ChemShorts article (April 1996 “LeakBusters”); also check June 2003 for a twist on helium vs. air balloons).
-------------
Reference (found through the National Science Foundation website): http://people.bxscience.edu/~chinyu/2690/exper/exp2.htm
Kids, how would you like to make your own rock? There are three major types of rock: sedimentary, metamorphic and igneous. This particular activity concerns sandstone, which is a type of sedimentary rock. You will need ½ cup (118 ml) of water, 2 paper cups, 2-1/2 tablespoons of Epsom salts (hydrated magnesium sulfate, MgSO4 which can be found at drugstores), and ½ cup (100 gm) of dry sand. Armed with these items you can perform your own geochemistry experiment!
Put 1-1/2 inches (4 cm) of water in one of the paper cups. Dissolve the Epsom salts in this water. Stir with a spoon until almost all the salt has dissolved. These salts will act to cement the particles of sand together, just like certain minerals cement sand grains together in real sandstone. Now put 1-1/2 inches (4 cm) of sand in the bottom of the other paper cup. Pour the salt mixture into the sand and stir until the sand is completely wet. Let this slurry sit undisturbed for an hour. Then carefully pour off any clear water that has risen to the top. Repeat this several times throughout the day as needed until no clear water is left. Now set the cup aside, uncovered, and let it sit undisturbed for at least one week.
When your sandstone has dried completely, you will be able to tear the paper cup away from it. If anything is still damp when you try this, let the sandstone dry for a few more days and then try again. This might seem like a long time to wait, but it is eons shorter than the time it takes for real sandstone to form!
In nature, all kinds of sediment – pebbles, sand, clay, tiny dead animals, shells, plants – can be turned into rock. Most sedimentary rocks form under water. The process may take millions of years as sediment is slowly buried by more piling on top. As the pile gets heavier, particles on the bottom are squeezed and warmed by the heat of the earth. In addition to that, water that has minerals dissolved in it seeps in between the pieces and then evaporates. The minerals that are left behind cement the particles together into a larger rock.
A geochemist can see the results of these processes using a microscope. Sedimentary rock grains are smoothed by their journeys through water and are surrounded by the mineral cements. Using a magnifying glass, see if you can make out any of these features. Igneous rocks, on the other hand, are jagged and interlocked without any cement.
-------------
References: “Geology Crafts for Kids: 50 Nifty Projects to Explore the Marvels of Planet Earth” by A. Anderson, G. Diehn, & T. Krautwurst. Sterling Publishing Co., NY, 1998, pg. 63. Also
http://www.coaleducation.org/lessons/sme/elem/17.htm.
Kids, how would you like to combine elements from both science and art to make a simulated stained glass? For artists, creating the right material (whether it is a painting or a sculpture or whatever) requires much experimentation until the result is exactly what they want. For some scientists this same principle holds when making a particular molecule, for example, although different tools and media are used. In this activity, you can experiment with the look of a colorful art material.
First, put about 1 tsp Elmer’s glue in a small plastic cup. Add about ¼ tsp water and mix with a popsicle stick. Pour the glue-water mixture into a yogurt cup lid or other plastic lid, or a Styrofoam bowl. Tilt the lid or bowl all around until the glue solution completely covers the inside surface. Next place two or three drops of differed food coloring onto the glue surface. Now, off to the side, put a small amount of liquid dish detergent in a small cup. Touch a toothpick into the detergent, getting just a very small amount, and then touch the center of each food coloring droplet and quickly remove the toothpick. Do not stir. What happens?
Your glue has water in it plus long-chain molecules called polyvinyl acetate. When the food coloring drops are added, they do not spread out much because of the polymer. (Try adding food coloring to a plain cup of water and you’ll see that it rather easily spreads out). When the detergent is added, the food coloring begins to spread out into the glue. This is because detergent molecules lessen the "pull" (the surface tension) between water and polymer molecules. The chemical word for soap that helps to describe this action is "surfactant". Experiment by touching the food coloring drops with more detergent, or with more or less colors to get the effect that you are looking for.
Think about this… Colored glass has been used for centuries to make beautiful stained glass windows. Glass makers use different combinations of chemicals to produce the many different colors of glass. Wonderful works of art are created by variations in the design, the colors, and the effect of light passing through the material. Can you think of a way to use your stained “glass” glue to make a design that light can shine through? Hint: wax paper might be a good surface to work on. Good luck!
Bonus information… Some of the pigments used to color glass are: cobalt oxide (CoO) makes blue, calcium fluoride (CaF2) makes milky white, gold (Au) or cuprous oxide (Cu2O) or selenium (Se) all make red glass. To make glass green, either iron sulfate (FeSO4) or copper (Cu) or chromium oxide (Cr2O3) are used. Amber glass is colored by a mixture of carbon (C) and iron sulfide (FeS). See the 12/96 issue of ChemShorts for an entire column devoted to glass itself.
-------------
Reference: “WonderNet! – Chemistry and Art” activity at: www.chemistry.org/portal/a/c/s/1/wondernetdisplay.html?DOC=wondernet\activities\art\stainedglass.html
Kids, how can you use chromatography to create your own colorful T-shirt design? In this activity, you will separate the ink from permanent colored markers to make a rainbow of colors on your T-shirt! Chromatography is a technique used to separate mixtures and can be used by chemists in fields as diverse as environmental studies to detect pollution in water and air to crime laboratories to identify clues such as blood, ink, or other substances found at a crime scene.
What do you do? First, review the information in the background section provided in the reference link below. You will need a coffee can, coffee filter or paper towel, a pre-washed t-shirt, permanent markers, rubbing alcohol, eye droppers, and a rubber band. Before you make a chromatogram on your T-shirt, practice with a coffee filter or paper towel. Rubber band the coffee filter or paper towel over the coffee can and draw a circle of colored dots on the coffee filter or paper towel. Using the eye dropper place a few drops of alcohol into the middle of the circle. As the alcohol spreads, watch the pattern the ink makes. The more alcohol you use, the farther the ink spreads; using less alcohol prevents the ink from spreading very far. Try any design you like, although the circle works best (a dotted circle forms a flower pattern). Repeat using your T-shirt instead of paper. Be sure that only one layer of the T-shirt (the back or front) is laid over the coffee can at one time. Let your T-shirt dry. Have a good time!
What’s going on here? Chromatography is a process used to separate mixtures. A substance is placed onto or into a medium and a solvent is passed through the test substance. In chromatography science, the solvent is called "the mobile phase" and the medium is called "the stationary phase". In this experiment, the medium is coffee filter paper or the t-shirt, the solvent is alcohol and our test substance is ink. Ink is a mixture; it is made of different substances mixed together. Parts of the test substance (the ink) may be attracted to the solvent (alcohol) and follow it up the medium (the coffee filter paper).
Have you ever mixed paint, crayons or food dye colors to create new colors? How do you make the color orange? Remember that yellow, red and blue are primary colors (they are not created by combining other colors). As you study the chromatographs and separate the ink colors, keep this information in mind. What do you think a chromatogram of orange or brown ink will look like, and does the result match your guess?
-------------
Reference: www.swe.org/iac/LP/tshirt_02.html (SWE is the Society of Women Engineers).
Finished T-Shirt example from the SWE page.
Kids, it’s that time of year again, right? When your teachers are asking you to think of science fair project ideas? One of the most common questions that I am asked is to provide ideas for science fair projects. Since we are all about chemistry here, this article is going to concentrate on projects that emphasize this particular science. You might be surprised at the vast array of topics that fit under this umbrella! There is a wonderful resource on the internet from Dr. Anne Marie Helmenstine, a chemist who actually keeps a chemistry blog at http://chemistry.about.com/b/a/202103.htm?nl=1
There she lists some resources to help you get an early start on your scientific masterpiece for this year, including helpful hints about:
There are also links provided to some excellent articles & resources at http://chemistry.about.com/od/sciencefairprojects/. Get help finding a subject, preparing a hypothesis, writing the report, and making a presentation for a science fair project. There is a guide that is suitable for grade school through university level. She also provides a collection of top-rated science fair project books and resources for students, parents, and educators. There are books that describe experiments, a CD-ROM with thousands of pages of ideas, and reference materials for making posters, giving presentations, and understanding the judging process.
So, armed with all of this information, let the games begin! I hope that you have a terrific time with all of your projects. (There are of course numerous sites on the internet about science fair projects, but this one might be a little off the beaten path and so we thought it was worth highlighting).
Kids, in this activity you can use some chemistry, your creativity, and a little muscle power to make a unique piece of artwork from a newspaper. You will need a newspaper with color pictures (like USA Today), scissors, vinegar, cotton swabs, a popsicle stick, white paper, and paper towels.
Use your scissors to cut out a small (5cm x 5cm or smaller) color picture or comic from the newspaper. Dip a cotton swab in vinegar and wipe it on the picture. Make sure you cover every part of the picture with vinegar. Place the picture between two paper towels and press hard for 5 or 10 seconds to dry off any excess vinegar. Place the picture face down on a piece of white paper. Place another piece of white paper on top and rub hard with the end edge of a popsicle stick. Make sure to rub over the entire picture. Lift the upper paper and then remove the piece of newspaper. You should have a transfer of the picture on the bottom white paper. What do you notice about the picture? Do you think there is enough ink left on the picture to make another transfer? Try it and see. Experiment with several different pictures on the same paper to make your own artistic creation.
What's going on here? The ink used on the newspaper is not easy to dissolve with water. This is good because the ink is less likely to smudge when the newspaper gets wet from rain or water spills. However, this ink will dissolve a bit better in a weak acid such as acetic acid, and vinegar is dilute acetic acid.
Here’s something a little bit different. Repeat the above activity except this time transfer something with words on it. What do you notice about the words on your transfer? Here's a way that you can make the words easier to read: Flip the paper over and use a cotton swab to rub a little baby oil on the back of the paper. What do you notice? Are the words easier to read now?
Think about this... The image you get after making a transfer is similar to what an artist gets by making a print. In both cases, the final image is the reverse of what was used to make it. To make a print, the artist uses special tools to scratch and carve the surface of a stone plate. Paint is rolled onto the stone and then paper is laid down on the paint. Absorbent material, such as felt, is placed on top of the paper and the entire stack of materials is put through a press. When the paper is lifted off the stone, it is a reversed image of what was carved into the stone. This means that for a print to come out the way the artist wants, the entire thing needs to be carved in reverse to begin with!
-------------
Reference: http://www.chemistry.org/portal/a/c/s/1/wondernetdisplay.html?DOC=wondernet\activities\art\collage.html (easier: Google “wondernet” to get “WONDERNET! Chemistry activities for kids, parents and teachers” and follow the links for Chemistry & Art.)
Updated 10/10/05
