Wednesday, March 26, 2008

Hand Warmers

(Click for larger image)

Lesson: Exothermic reactions produce heat
What Happened: Iron powder began oxidizing (rusting) when exposed to the air, becoming hot

Bought these packets at Wal-Mart a few months ago and figured it was time to open one up and see what would happen. The "all-natural" ingredients seemed pretty safe to mess around with.

As soon as I poured the powder into the mason jar, it started to heat up. I don't know how hot it got (Note to self: Get thermometer!) but I suspect it was hotter than the temperatures listed above, because it didn't last as long. Probably because it was exposed to more air than if I had left it in the air-permeable packet. It may have dried out quicker, too.

Although you can't see it in the picture at the top, there was smoke coming out of the jar. We also tried mixing some with a little more water to see what happened. The heating process stopped. However, when I dipped a magnet into the resulting goop it did act a little like ferrofluid.

What's going on (from Camping Survival):
The heating process takes place in this fashion:
  1. The iron in the pouch, when exposed to oxygen, oxidizes and therefore produces heat (aka, "Air Activated").
  2. When iron oxidizes it produces iron oxide, more commonly referred to as rust.
  3. The salt acts as a catalyst.
  4. The carbon [activated charcoal] helps disperse the heat.
  5. The vermiculite [the shiny mica-like specks] acts as an insulator for the purpose of retaining the heat and the cellulose is added as a filler.
  6. All of these ingredients are surrounded by a polypropylene bag.
  7. Polypropylene allows air to permeate the ingredients while holding in moisture.
And the chemical equation (from Curriki, which tells you how to mix up your own):
Hand warmers work because of a rusting process. The rusting is a redox reaction and the equation is as follows: 4Fe(s) + 3O2(g) -> 2Fe2O3(s) .

Sunday, March 23, 2008

Peeps Chemistry

There is a long and glorious tradition of torturing leftover Easter candy. At the site Peep Research, the fear response of a Marshmallow Peep is measured through exposure to heat in a microwave. But many of the more sophisticated Peeps experiments can probably not be done at home. While you can replicate the vacuum experiment above (by Seaford, NY chemistry teacher Edward Kent, who has many other interesting demonstration videos on his website) by using an ordinary Kitchen Vacuum Packer as shown on the Steve Spangler website, the explosive liquid oxygen video should be only be done under laboratory conditions.

More Peepy links at Peep-O-Rama including Martha Stewart's recipe for fresh, homemade Peeps (sort of an oxymoron). Also solubility tests by a stuffed chemistry mascot mole.

Oh, and here's the chemistry explanation, from the Exploratorium's Science of Cooking website:

Marshmallows are mostly sugar and water wrapped around a bunch of air bubbles. When you cook marshmallows in your microwave oven, several things happen at once. The microwave makes the water molecules vibrate very quickly—which makes the water heat up. The hot water warms the sugar, which softens a little. The hot water also warms the air bubbles.
When you warm air in a closed container, the gas molecules move around faster and push harder against the walls of the container. As the air in the bubbles warms up, the air molecules bounce around faster and faster and push harder against the bubble walls. Since the sugar walls are warm and soft, the bubbles expand, and the marshmallow puffs up. If it puffs up too much, some air bubbles burst, and the marshmallow deflates like a popped balloon.
When you take the marshmallow out of the microwave and it cools off, the bubbles shrink and the sugar hardens again. When the microwave marshmallow cools, it’s dry and crunchy. We think that’s because some of the water in the marshmallow evaporates when the marshmallow is hot. If you cook your marshmallow for too long, it turns brown or black inside. That happens when the sugar gets so hot that it starts to burn [known as caramelizing].

Saturday, March 22, 2008

Baking soda vs. baking powder

Apricot, Poppy, and Chocolate Kiss filled Hamantaschen

We made Hamantaschen cookies for Purim and the question came up about the difference between baking soda and baking powder. We have done the baking soda and vinegar thing many times, so we already know that mixing sodium bicarbonate with an acid releases carbon dioxide. When you bake, those little bubbles of CO2 make the bread puff up. The acid needed to start the reaction in a batter can come from yogurt, buttermilk, lemon juice, or even molasses or honey.

Baking powder is baking soda with the acid already mixed in, in the form of cream of tartar. When moistened, powdered acid combines with the baking soda and produces the requisite bubbles. Some baking powder is "double acting," meaning it releases most of the bubbles when heated, so that the leavening action doesn't expend itself while the dough is waiting on the counter to bake.

Baking powder and water fizzing

There are many explanations on the web about this topic, but I like this one from something called Wally's Food Company. Scroll down to read the chemical explanation of why baking soda absorbs odors in the refrigerator.

Tartaric acid

Thursday, March 13, 2008

Breaking Molecular Bonds - Jello and Pineapple

Lesson: Breaking molecular bonds in protein using enzymes
What Happened: We disintegrated Jello using pineapples

(With help from Anthony)

The ingredients

Before we added the pineapple

The Jello started to melt after a minute

The Jello was half dissolved by now


The Jello is almost fully dissolved by now

It's fully dissolved now

Warning: Do not add pineapple

Why did it do that?

(From Chempedia)

Jell-O gelatin was first patented in 1845 by Peter Cooper of Cooper Union.

Gelatin is a processed version of the protein collagen, a simple protein that makes up one-third of all proteins in the human body. The main source of the collagen that is used in Jell-O comes from hooves, bones, connective tissue found on cows, horses and pigs. Along with collagen, Jell-O consists of water, food coloring, sugar, and artificial flavors. Collagen is found in all living animals. This protein is what gives body parts strength, flexibility, and protection. There are five major categories of collagen that range from the fibers in your eyes to the structure of placentas. To harvest the collagen needed for gelatin the Jell-O Corporation turns to natural sources found in cows, horses, and pigs. The animals' body part's which were previously mention are ground up to expose the proteins within. After they are ground up the bio matter is then treated with a strong acid or base, which breaks down the cellular structures of the collagen to release the proteins from connective tissue. After the proteins become separated from the tissues the bio-mass is then discarded. Then, the mixture created from the released proteins (collagen proteins, which are the basis of Jell-O) and the strong acid or base is then boiled.

(From General Chemistry Online)
Pineapple contains a plant enzyme called bromelain that breaks down proteins. Bromelain is used in many meat tenderizers for this purpose (and that's why cooking ham with pineapple makes it tender). JellO packages warn you not to put pineapple chunks into the gelatin. Jello is a protein mesh with trapped pockets of liquid; the bromelain cuts the protein chains and keeps the gelatin from jelling properly. Why do pineapples produce an enzyme that tenderizes meat? It's a defense mechanism. The sap of the pineapple plant contains much higher concentrations of bromelain and can cause severe pain if eaten.

Other uses for bromelain:

(From Wikipedia)
Bromelain can be used in a vast array of medical conditions. It was first introduced in this area in 1957, and works by blocking some proinflammatory metabolites that accelerate and worsen the inflammatory process. It is an anti-inflammatory agent, and so can be used for sports injury, trauma, arthritis, and other kinds of swelling. Its main uses are treatment of athletic injuries, digestive problems, phlebitis, sinusitis, and aiding healing after surgery.

Monday, March 10, 2008

Light and Chemistry - Triboluminesence

Lesson: Breaking molecular bonds can release energy in the form of light
What Happened: We crunched Altoids in a dark room and saw blue-white sparks.

Traditionally, this demonstration is done with Wint-O-Green Lifesavers -- but the package I found at the supermarket listed only artificial ingredients. What makes the candy spark visible is the fluorescent property of wintergreen's aromatic essence, methyl salicylate. So we tried Altoids and Canada Mints. At night, we went into the bathroom (so we could see ourselves in the mirror), turned off the lights and waited a few minutes for our eyes to adjust to the dark. The Altoids worked well. The Canada Mints are slightly more chewy and hence, did not crunch well.

The website How Stuff Works explains the process like this:
Triboluminescence occurs when molecules, in this case crystalline sugars, are crushed, forcing some electrons out of their atomic fields. These free electrons bump into nitrogen molecules in the air. When they collide, the electrons impart energy to the nitrogen molecules, causing them to vibrate. In this excited state, and in order to get rid of the excess energy, these nitrogen molecules emit light -- mostly ultraviolet (nonvisible) light, but they do emit a small amount of visible light as well. This is why all hard, sugary candies will produce a faint glow when cracked.
Although it was fun to watch the bright flashes of light in our mouths, we had to stop after a few candies because the sharp mintiness got to us.

A photo of the flash, from Wayne's This and That:

Interestingly, as I learned from Wikipedia, methyl salicylate, or C6H4(HO)COOCH3, is what gives Ben-Gay its minty heat. It can cause poisoning and even death when eaten or applied to the skin in large amounts.

Curiously strong, indeed.

Sunday, March 9, 2008

The Problem with Homeschool Science Resources

Way back in November, I got a comment about finding hard-to-locate chemicals from Ruth in NC, whose own blog is Traveling Jews, suggesting that I try a company called Home Science Tools. I checked out their website, and was pretty impressed. In fact, we got a microscope from them for the holidays.

But I couldn't bring myself to add them to the sidebar list of suppliers, because of books like the one shown here -- biology curriculum from places like Bob Jones and "God's Design" that teach creation "along with evolution." (If you think this issue just affects homeschoolers, though, see my related blog posts here and here.)

Interestingly, parents whose children have used these texts say their kids score very well on standardized science entry exams for college. (I wonder whether that's a comment on what the tests include...)

I realize that so far, despite the number of resources I've turned up, our chemistry studies this year have stayed on a pretty superficial level. There are lots of homeschoolers who are going through much more rigorous courses than I am. So, what programs do your kids use? How have they worked out?

Wednesday, March 5, 2008

More Light and Chemistry-A Homemade Spectroscope

In Oliver Sacks' book Uncle Tungsten: Memories of a Chemical Boyhood, he describes walking around with a pocket spectroscope, observing the bright and dark lines in the spectra of different types of light sources.

Instead of buying the lovely model above from Educational Innovations, however, we followed Simon Quellen Field's directions for a home-made spectroscope on his website (It's also in his book,Gonzo Gizmos: Projects & Devices to Channel Your Inner Geek.)

Here's Field's explanation of what's going on:

A spectroscope is a device that lets us find out what things are made of. It works by taking light and splitting it up into its component colors. Different elements make different colors when they glow. We can make objects and gasses glow by heating them up in a flame, or by passing electricity through them. The spectroscope spreads out the colors of the light, and we can identify the elements by the bright lines we see in the spectroscope.
We pretty much followed Field's directions, except for using duct tape instead of aluminum tape.

The razor blade slit, which is where the light comes in, was also finished off with duct tape. I forgot to take a picture of the placement of the DVD; we measured the distance from the slit to the end of the box and marked a line for the left edge of the disc. (See Field's directions to figure out what I'm talking about.)

We used it on incandescent and fluorescent bulbs and sunlight, and it seems to work pretty well. I noticed that along with the spectrum, you get a pinhole camera effect. We'll have to find some other light sources to test it out on.

Saturday, March 1, 2008

Black Light

From's Chemistry Page

There are a lot of everyday materials that fluoresce, or glow, when placed under a black light. A black light gives off highly energetic ultraviolet light. You can't see this part of the spectrum, which is how 'black lights' got their name. Fluorescent substances absorb the ultraviolet light and then re-emit it almost instantaneously. Some energy gets lost in the process, so the emitted light has a longer wavelength than the absorbed radiation, which makes this light visible and causes the material to appear to 'glow'. Fluorescent molecules tend to have rigid structures and delocalized electrons.
(The black light fluorescent bulb, with holder, was $10 at Wal-Mart. It can be plugged in and moved around wherever needed. We also have an incandescent black light bulb, but it doesn't work very well, and gets very hot.)

What we got to glow:

White Paper

White paper is treated with fluorescent compounds to help it appear brighter and therefore whiter. Sometimes forgery of historical documents can be detected by placing them under a black light to see whether or not they fluoresce. White paper made post-1950 contains fluorescent chemicals while older paper doesn't.

Tonic Water

The bitter flavoring of tonic water is due to the presence of quinine, which glows blue-white when placed under a black light.

Laundry Detergent

Some of the whiteners in detergent work by making your clothing a bit fluorescent. Even though clothing is rinsed after washing, residues on white clothing cause it to glow bluish-white under a black light. Blueing agents and softening agents often contain fluorescent dyes, too. The presence of these molecules sometimes causes white clothing to appear blue in photographs.

What we didn't get to glow:


Vitamin A and the B vitamins thiamine, niacin, and riboflavin are strongly fluorescent. Try crushing a vitamin B-12 tablet and dissolving it in vinegar. The solution will glow bright yellow under under a black light.


Chlorophyll makes plants green, but it fluoresces a blood red color. Grind some spinach or swiss chard in a small amount of alcohol (e.g., vodka or everclear) and pour it through a coffee filter to get chlorophyll extract (you keep the part that stays on the filter, not the liquid). You can see the red glow using a black light or even a strong fluorescent bulb, such as an overhead projector lamp, which (you guessed it) gives off ultraviolet light.


Minerals and gemstones are most commonly made fluorescent or phosphorescent due to the presence of impurities. A sample of sodalite I bought at the New York State Museum back during Chemistry Week in October came with a slip of paper said "many" specimens are fluourescent; ours was not.

(A transparent piece of what I think is agate did glow a nice orange color, but it came out bluish in the photo.)

Might try next time:

Postage stamps
Tooth whiteners
Dollar bills
Petroleum jelly
Solar beads
And making bubble juice out of fluorescent soap!

What glowed that we weren't expecting: