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Do Radioactive Elements Really Glow?

2012-02-16T08:14:47Z

In books and movies you can tell when an element is radioactive because it glows. Movie radiation usually is an eerie green phosphorescent glow or sometimes a bright blue or deep red. Do radioactive elements really glow like that?

The answer is both yes and no. First let's take a look a the 'no' part of the answer. Radioactive decay may produce photons, which are light, but the photons are not in the visible portion of the spectrum. So no... radioactive elements do not glow in any color you can see.

On the other hand, there are radioactive elements that impart energy to nearby phosphorescent or fluorescent materials and thus appear to glow. Radium and tritium are mixed with phosphorescent materials so that the ionizing radiation from the radioactive elements can excited the electrons in the phosphors, exciting them to a higher energy level. As the electrons return to a lower energy level, visible light is produced.

If you saw plutonium it might appear to glow red. Why? The surface of plutonium burns in the presence of oxygen in the air, like an ember of a fire.

Another example of an element that glows is radon. Radon ordinarily exists as a gas, but as it is cooled it becomes phosphorescent yellow, deepening to glowing red as it is chilled below its freezing point.

Actinium is another radioactive element that glows. Actinium is a radioactive metal that glows pale blue.

While not all radioactive elements glow, there are examples of glowing elements. The elements usually do not glow green as in movies -- that color likely comes from the common phosphor color used with radium and tritium, plus it is a color that shows up really well when it is filmed.

Glowing Radioactive Materials Photo Gallery | Do Radioactive Elements Glow in the Dark

Do Radioactive Elements Really Glow? originally appeared on About.com Chemistry on Thursday, February 16th, 2012 at 08:14:47.

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This Day in Science History - February 16 - Julius Thomsen

2012-02-15T22:05:22Z

February 16^th is Julius Thomsen's birthday. Thomsen was a Dutch chemist who first identified a need for a period on the periodic table with a valence number of zero. His reasoning was based on how some periods had positive valences and others had negative valence, so there must be a period where the transition occurs between positive and negative. He also predicted these elements should have atomic weights of 4, 20, 36, 84, and 132.

His hypothesis would be later be shown to be correct. In 1895, Carl von Linde would discover these elements and call them the noble gases. Find out more about Thomsen and what else occurred on this day in science history.

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This Day in Science History - February 16 - Julius Thomsen originally appeared on About.com Chemistry on Wednesday, February 15th, 2012 at 22:05:22.

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Wordless Wednesday - Rainbow in a Glass

2012-02-15T12:34:45Z

This pretty rainbow density column only requires sugar, water and food coloring!

Wordless Wednesday - Rainbow in a Glass originally appeared on About.com Chemistry on Wednesday, February 15th, 2012 at 12:34:45.

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How Haircoloring Works

2012-02-15T07:42:30Z

Over 75% of women and a growing percentage of men color their hair. Do you know how haircoloring works?

In the Beginning

The first safe commercial haircolor was created in 1909 by French chemist Eugene Schuller, using the chemical paraphenylenediamine. How does haircolor work? It's the result of a series of chemical reactions between the molecules in hair, pigments, as well as peroxide and ammonia, if present.

What is Hair?

Hair is mainly keratin, the same protein found in skin and fingernails. The natural color of hair depends on the ratio and quantities of two other proteins, eumelanin and phaeomelanin. Eumelanin is responsible for brown to black hair shades while phaeomelanin is responsible for golden blond, ginger, and red colors. The absence of either type of melanin produces white/gray hair.

Natural Colorants

People have been coloring their hair for thousands of years using plants and minerals. Some of these natural agents contain pigments (e.g., henna, black walnut shells) and others contain natural bleaching agents or cause reactions that change the color of hair (e.g., vinegar). Natural pigments generally work by coating the hair shaft with color. Some natural colorants last through several shampoos, but they aren't necessarily safer or more gentle than modern formulations. It's difficult to get consistent results using natural colorants, plus some people are allergic to the ingredients.

Temporary Hair Color

Temporary or semi-permanent haircolors may deposit acidic dyes onto the outside of the hair shaft or may consist of small pigment molecules that can slip inside the hair shaft, using a small amount of peroxide or none at all. In some cases, a collection of several colorant molecules enter the hair to form a larger complex inside the hair shaft. Shampooing will eventually dislodge temporary hair color. These products don't contain ammonia, meaning the hair shaft isn't opened up during processing and the hair's natural color is retained once the product washes out.

How Lightening Works

Bleach is used to lighten hair. The bleach reacts with the melanin in hair, removing the color in an irreversible chemical reaction. The bleach oxidizes the melanin molecule. The melanin is still present, but the oxidized molecule is colorless. However, bleached hair tends to have a pale yellow tint. The yellow color is the natural color of keratin, the structural protein in hair. Also, bleach reacts more readily with the dark eumelanin pigment than with the phaeomelanin, so some gold or red residual color may remain after lightening. Hydrogen peroxide is one of the most common lightening agents. The peroxide is used in an alkaline solution, which opens the hair shaft to allow the peroxide to react with the melanin.

Permanent Hair Color

The outer layer of the hair shaft, its cuticle, must be opened before permanent color can be deposited into the hair. Once the cuticle is open, the dye reacts with the inner portion of the hair, the cortex, to deposit or remove the color. Most permanent hair colors use a two-step process (usually occurring simultaneously) which first removes the original color of the hair and then deposits a new color. It's essentially the same process as lightening, except a colorant is then bonded within the hair shaft. Ammonia is the alkaline chemical that opens the cuticle and allows the hair color to penetrate the cortex of the hair. It also acts as a catalyst when the permanent hair color comes together with the peroxide. Peroxide is used as the developer or oxidizing agent. The developer removes pre-existing color. Peroxide breaks chemical bonds in hair, releasing sulfur, which accounts for the characteristic odor of haircolor. As the melanin is decolorized, a new permanent color is bonded to the hair cortex. Various types of alcohols and conditioners may also be present in hair color. The conditioners close the cuticle after coloring to seal in and protect the new color.

Why Hair Turns Green from a Pool &124; Can Hair Turn White Overnight?

How Haircoloring Works originally appeared on About.com Chemistry on Wednesday, February 15th, 2012 at 07:42:30.

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This Day in Science History - February 15 - Galileo Galilei

2012-02-14T22:05:36Z

February 15^th is Galileo Galilei's birthday. Galileo was an Italian natural philosopher who was key figure at the beginning of the scientific revolution and made several major contributions to its progress.

Before Galileo, science was not considered a profession. Typically, people who did 'science' were considered natural philosophers and held positions as medical doctors, mathematicians or priests with extra time on their hands. The name philosopher was typically used because it was just as likely for someone to explain a phenomenon by what they believed happened through other philosophies or their own ideas as easily as their own observations.

Galileo was one of the first to break away from Aristotle's four terrestrial elements of earth, air, fire and water with a new basic element of corporeal matter. He was the first to express the belief that the basic laws of science could be broken down into mathematics. He was among the first to take a closer look at the skies above with a telescope.

His life is generally used as the beginning point of the history of modern science. His philosophy of observe first, explain second and observe some more would become the foundation of the modern scientific method. Find out what else occurred on this day in science history.

This Day in Science History - February 15 - Galileo Galilei originally appeared on About.com Chemistry on Tuesday, February 14th, 2012 at 22:05:36.

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Can You Pass a 3rd Grade Science Test?

2012-02-14T16:02:54Z

Several readers wrote in about the 6th grade science quiz that I posted, commenting on the state of modern science education and about the questions that were missed most often. This week's quiz is based on science standards for the 3rd grade. I'll warn you in advance that there is one question that has an answer that is different from what you might have learned. Otherwise, I think the quiz is pretty straightforward. Are you ready to give it a try?

Can You Pass a 3rd Grade Science Test? originally appeared on About.com Chemistry on Tuesday, February 14th, 2012 at 16:02:54.

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Keep Valentine's Day Flowers Fresh

2012-02-14T08:17:29Z

Presenting a bunch of wilted flowers on Valentine's Day may not convey the right message, unless that message runs along the lines of 'My love for you has faded, like these pathetic flowers' or 'See, I got you something for Valentine's Day, but I'm not out to impress you." I'd suggest cutting the heads off of the flowers or maybe giving black flowers if the former sentiment applies. If your heart is in the right place, however, either keep your flowers healthy or consider giving a different gift.

If you get Valentine's Day flowers from a florist, they probably include a packet of floral preservative, but if you pick flowers yourself or decide to custom-color them, you may want to make up some floral preservative to help keep your flowers fresh and beautiful. Though you can pay a lot for pre-packaged flower preservative, it's really easy and economical to make it yourself. Your preservative needs to contain water, food for the flowers, and a disinfectant to prevent bacteria, mold, and fungi from growing. Possibly the easiest way to make flower food is to mix together a can of Sprite™ (or other non-cola carbonated soft drink), refill the can with water, and add a splash of household bleach. If you don't have those ingredients handy, I have additional recipes for floral preservatives that you can try. Trim the stems of your flowers at an angle and underwater (so tiny air bubbles don't stick on the stems and prevent water from moving in). Flowers with long stems, like tulips, will benefit from having support for the first couple of hours after you put them in water. Either leave the flowers in their wrapping for loosely tie them together. You can remove the support once the stems are hydrated and strong. Keep your flowers in a cool location, preferably out of direct sunlight. Most flowers will last about a week if they are given proper care.

Keep Valentine's Day Flowers Fresh originally appeared on About.com Chemistry on Tuesday, February 14th, 2012 at 08:17:29.

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This Day in Science History - February 14 - Julius Nieuwland

2012-02-13T22:05:49Z

February 14^th is the birthday of Julius Nieuwland. Nieuland was a Belgian priest and chemist who's research into the chemistry of acetylene directly led to the first commercially successful artificial rubber, polychloroprene. This is better known by DuPont's trademark, neoprene.

Nieuwland discovered he could polymerize acetylene into a rubber-like jelly of divinyl acetylene. The story might have ended there except Elmer Bolton of DuPont attended a lecture of Nieuwland's. Many industries were looking for an alternative source of rubber. Rubber is a natural product produced from latex of the para rubber tree. The majority of the world's rubber came from plantations in the Amazonian rainforest. Chemical engineers around the world were trying to discover a useful synthetic alternative. Bolton acquired the rights to further develop Nieuwland's discovery for DuPont. Scientists at DuPont collaborated with Nieuwland to produce neoprene.

Nieuland is also known for his discovery of the chemical weapon lewisite. He discovered the reaction during his acetylene research, but abandoned further research because of it's poisonous nature. When his research was weaponized to produce lewisite, he nearly gave up chemical research entirely. Find out what else occurred on this day in science history.

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This Day in Science History - February 14 - Julius Nieuwland originally appeared on About.com Chemistry on Monday, February 13th, 2012 at 22:05:49.

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This Day in Science History - February 13 - Étienne Geoffroy

2012-02-12T22:10:59Z

February 13^th is Étienne François Geoffroy's birthday. Geoffroy was a French physician and chemist who was the first to arrange the known elements into a table based on their chemical affinity to each other.

Anyone who has ever mixed two items together knows some things combine better than others. In chemistry, two different chemical species' affinity is a property that shows how likely a chemical reaction will occur when mixed. Reagents with strong affinity are more likely to react with each other than reagents with little affinity to each other. Geoffroy's table had a series of reagents across the top with other reagents with high affinity with these elements listed below. This table became a standard table for 18th Century chemists until the end of the century when it was shown the amount of a reagent drove the reaction.

Find out what else occurred on this day in science history.

This Day in Science History - February 13 - Étienne Geoffroy originally appeared on About.com Chemistry on Sunday, February 12th, 2012 at 22:10:59.

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How To Cook a Frozen Pizza on the Stove - Science Experiment

2012-02-12T19:50:53Z

So, the other day I found myself in a hotel room with a frozen pizza and a stove, but no oven. I did what any hungry scientist would do. I set out to determine whether or not it was possible to cook a frozen pizza on the stove. In order for the experiment to be a success, the pizza had to be good enough to eat. Well, also I would have considered the experiment a failure if there had been a fire. That is not generally a condition of failure in my projects, but when I'm on the road I'm a little less of a pyro.

Anyway, I wrote up the project in terms of the scientific method because I think this is the sort of everyday science that people can relate to more easily than an experiment using hard-to-pronounce chemicals... Let's cook pizza!

How To Cook a Frozen Pizza on the Stove - Science Experiment originally appeared on About.com Chemistry on Sunday, February 12th, 2012 at 19:50:53.

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