Chemistry

May 23^rd is American physicist John Bardeen's birthday. He was awarded the Nobel Prize in Physics on two different occasions. The first prize was in 1956 for being part of the team that developed the semiconductor transistor. The second was in 1972 for his role in formulating the BCS theory of superconductivity. Bardeen is one of four people to have won two different Nobel Prizes. Marie Curie, Linus Pauling and Frederick Sanger are the other three people who share this honor.

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I think my problem, this particular one anyway, started in grade school. In art class, we'd use a toothpick to mix a bit of paint into clear-drying school glue and adorn skin, clothes, desks, everything with glue 'jewels'. I grew careless with glue. After all, soap and water could handle any mess.

When Super Glue entered my life, I treated it casually. So, if you can stick it together (accidentally) with Super Glue, I've stuck it. Fingers, lips, hair, clothes, carpeting. It doesn't wash off. Fortunately, you can remove Super Glue from your skin and clothes. All you need is one household chemical, acetone, which you can find in some nail polish removers. Work the acetone into clothing or dab it onto skin with a cotton swab and it dissolves the glue. Acetone doesn't work for everything. For example, it dissolves acrylic as easily as the acrylate in the glue, plus you need to take other steps if you Super Glue your eyeballs or your mouth.

Tracing paper is translucent paper that you place over printed material or a drawing so you can trace over it. Would it surprise you to learn that tracing paper is essentially regular white paper?

The reason ordinary paper is opaque is because the air trapped between the cellulose fibers in paper scatters light. One way to make tracing paper is to press the air out of paper. Another method is to make paper from pulp that has been beaten in water long enough to divide and hydrolyze the cellulose fibers. A third way to make tracing paper involves a chemical process. When paper is soaked in sulfuric acid for a few seconds, rinsed, and dried, some of the cellulose is converted into a gelationous amyloid form.

No matter which process is used, tracing paper tends to be lighter and stronger than original paper. It's also lower in humidity and resists water damage.

Make Your Own Paper | Make Marbled Paper

Did you know that you can make a polymer from an element? It's really easy to turn ordinary yellow sulfur into plastic sulfur! As an added bonus, you'll get to experience a couple other interesting properties of sulfur. The yellow solid melts into a blood-red liquid. When it is heated, it may ignite with a blue flame... Make plastic sulfur

On May 22, 1969, NASA's Apollo 10 mission conducted the lunar module separation test and orbited the moon as a dress rehearsal for the Apollo 11 moon landing in July. Thomas Stafford and Eugene Cernan boarded the Snoopy lunar module and detatched from the command module and descended into a low lunar orbit. At closest approach, Snoopy came within 15 miles of where Apollo 11 would land. They reattached to the command module and returned to Earth.

This mission would have had to have been one of the most difficult missions to accomplish as an astronaut. They climbed aboard a fully equipped rocket, flew to the moon, got close to the landing point but purposely returned to the command module and came home. This seems about the same as getting in a car in New York City, driving to San Francisco's Fisherman's Wharf, seeing some great restaurants from the car as you drive by, returning to New York and telling the next crew all about the fish lunch specials you saw, how the car worked great and that there was plenty of parking.

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Color change chem demos are interesting and popular, but many of them require hard-to-find chemicals. Yet, all you need is a red or purple cabbage to set up a color change demo that kids can perform! Get red cabbage juice by boiling shredded cabbage in a small amount of water or microwaving it. The juice is a natural pH indicator, which changes color in response to acids and bases. You can change the color of the juice as if by magic:

1. Fill a small glass about 3/4 full of the cabbage juice solution. If it's too dark, you can add water.

2. In another glass, add a few drops of another chemical. Use ammonia to turn the liquid green, lemon juice or vinegar to turn it red, or baking soda to turn it blue.

3. When you're ready to do your 'trick', pour the juice into the apparently empty glass.

More Cabbage Juice Projects

Red Cabbage pH Paper
Fried Green Eggs
pH Rainbow

Pharaoh's snakes or pharaoh's serpents are a type of small firework in which a lighted tablet exudes smoke and ash in a growing column which resembles a snake. The modern version of this firework is the non-toxic black snake. Pharaoh's snakes produce a more spectacular display, but they are toxic so now this firework is only produced as a chemistry demonstration. If you have the materials and a fume hood, you may wish to make your own Pharaoh's snakes.

Making Pharaoh's Snakes

This is an extremely simple firework demonstration. All you need to do is ignite a small pile of mercury(II) thiocyanate, Hg(SCN)₂. Mercuy thiocyanate is an insoluble white solid which can be purchased as a reagent or can be obtained as a precipitate by reacting mercury(II) chloride or mercury(II) nitrate with potassium thiocyanate. All mercury compounds are toxic, so the demonstration should be performed in a fume hood. Typically the best effect is obtained by forming a depression in a shallow dish full of sand, filling it with mercury(II) thiocyanate, lightly covering the compound, and applying a flame to initiate the reaction.

Pharaoh's Snakes Chemical Reaction

Igniting mercury(II) thiocyanate causes it to decompose into an insoluble brown mass that is primarily carbon nitride, C₃N₄. Mercury(II) sulfide and carbon disulfide are also produced.

2Hg(SCN)₂ → 2HgS + CS₂ + C₃N₄

Flammable carbon disulfide combusts to carbon(IV) oxide and sulfur(IV) oxide:

CS₂ + 3O₂ → CO₂ + 2SO₂

The heated C₃N₄ partially breaks down to form nitrogen gas and dicyan:

2C₃N₄ → 3(CN)₂ + N₂

Mercury(II) sulfide reacts with oxygen to form mercury vapor and sulfur dioxide. If the reaction is performed inside a container, you will be able to observe a gray mercury film coating its interior surface.

HgS + O₂ → Hg + SO₂

Although Pharaoh's snakes are considered a type of firework, they do not explode or even emit sparks. They burn on the ground and release smoky vapors. All aspects of the reaction can be hazardous, including handling the mercury thiocyanate, breathing the smoke or touching the ash column, and contact with the remains of the reaction during clean-up. If you perform this reaction, use appropriate safety precautions for dealing with mercury.

May 21^st was the birthday of two men who invented two electric diagnostic devices that are often confused with each other. The EEG, or electroencephalogram device, was invented by German psychologist Hans Berger to record electrical signals from the brain. The ECG or EKG, otherwise known as electrocardiogram was invented by Dutch physician Willem Einthoven to measure the electrical current given off by heart beats.

Perhaps nobody mixes these two devices up, but I sometimes do. All you have to remember: EEG - brain waves, ECG or EKG - heart beats.

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Here's a fun and fiery chemistry demonstration for you. Melt potassium nitrate (KNO₃) in a test tube. Flaming the test tube with a gas burner works well. Decomposition of the potassium nitrate releases oxygen (O₂).

2 KNO₃ → 2 KNO₂ + O₂

Take a piece of charcoal that is small enough to fit inside the test tube. Flame it with the burner to heat it and drop it into the test tube. Rapid combustion of the charcoal will occur as the carbon in the charcoal reacts with the oxygen liberated by the potassium nitrate.

C + O₂ → CO₂

The piece of charcoal will bounce around inside the test tube or 'dance' as it is oxidized.

Dancing Gummi Bear Demo | Instant Fire Demo

A heavy metal, in the general sense, is a metal which is toxic and has a high density, specific gravity or atomic weight. Examples of heavy metals include lead, mercury and cadmium.

Misleading Term?

However, according to the International Union of Pure and Applied Chemistry or IUPAC, the term "heavy metal" may be a "meaningless term" because there is no standardized definition for a heavy metal. Some light metals or metalloids are toxic, while some high-density metals are not. For example, cadmium generally is considered a heavy metal, with an atomic number of 48 and specific gravity of 8.65, while gold typically is not toxic, even though it has an atomic number of 79 and specific gravity of 18.88. For a given metal, the toxicity varies widely depending on the allotrope or oxidation state of the metal. Hexavalent chromium is deadly; trivalent chromium is nutritionally significant in many organisms, including humans.