Tuesday, July 4, 2017

Facts about Fireworks

Behind the scenes of the dazzling light shows that make spectators "Ooh!" and "Ahh!" on the Fourth of July, are carefully crafted fireworks. Whether red, white and blue fountains or bursts of purple sparks, each firework is packed with just the right mix of chemicals to create these colorful lights.
Inside each firework is something called an aerial shell -  a tube that contains gunpowder and dozens of small modules called "stars," which measure about 1 to 1.5 inches (3 to 4 centimeters) in diameter, according to the American Chemical Society (ACA). These stars hold fuel, an oxidizing agent, a binder and metal salts or metal oxides - the source of the firework's hues. A time-delay fuse ignites the gunpowder and bursts the aerial shell once the firework is midair, causing the stars to scatter and explode far above the ground, producing a shower of light and color.

Once exposed to fire, the stars' fuel and oxidizing agents generate intense heat very rapidly, activating the metal-containing colorants. When heated, atoms in the metal compounds absorb energy, causing their electrons to rearrange from their lowest energy state to a higher "excited" state. As the electrons plummet back down to their lower energy state, the excess energy gets emitted as light.

Each chemical element releases a different amount of energy, and this energy is what determines the color or wavelength of the light that is emitted. For instance, when sodium nitrate is heated, electrons in the sodium atoms absorb the energy and get excited. As the electrons come down from the high, they release their energy, about 200 kilojoules per mole (a unit of measurement for chemical substances) or the energy of yellow light, according to the website of the University of Wisconsin-Madison chemistry professor Bassam Z. Shakhashiri.
The recipe that creates blue includes varying amounts of copper chloride compounds. Red comes from strontium salts and lithium salts, and the brightest red is emitted by strontium carbonate, the ACA explained on their website.
Just like paints, secondary colors are made by combining the ingredients of their primary-color relatives. A mixture of blue-producing copper compounds and red-producing strontium compounds results in purple light, the ACA reported.
Fireworks have been around for hundreds of years, and over the centuries experts known as pyrotechnic chemists have developed combinations of chemicals that not only produce breathtaking visual displays in a range of shapes and colors, but which are stable and can be used safely, chemist John Conkling, a fireworks expert at Washington College in Maryland, told the ACA.

Fireworks have a history going back to ancient China, long before the Founding Fathers led the United States to independence. But patriotic pyrotechnics have become deeply ingrained in the American tradition, with huge annual shows planned from New York Harbor to San Francisco Bay.

Every year as Fourth of July celebrations get underway in the U. S.,  the sound and sparkle of fireworks will be inescapable across much of the country. Here are five facts you might not know about those brilliant blasts:

The pyrotechnics depend on science

There's a bit of chemistry behind the vibrant colors that burst in fireworks displays. Each firework contains pellets, called "stars," which have hue-altering elements. Barium glows green; copper burns blue; calcium makes orange; and sodium, yellow. As for those weeping willow-like displays? Longer-burning gold or silver can make a nice trailing effect. And the ones that seem to crack and sizzle often contain some sort of flash powder, like magnesium perchlorate.

The different shapes fireworks take - from smiley faces to flags to planets - depend on the pattern of the pellets inside the shell. Pattern shells were first used in the early 1990s in Washington, D.C., to greet returning Desert Storm troops, creating fireworks that burst in purple hearts and yellow bows. One of the latest innovations in fireworks patterns is the ability to light up the sky with cube-shaped explosions, though designers continue to roll out new, amazing shapes.

The biggest ever displays haven't been in America

Despite America's penchant for pyrotechnics around this time of year, the Guinness World Record for the largest fireworks display goes to Kuwait. On November 10th, 2012, 77,282 individual fireworks were launched over a 3-mile-long (5 kilometers) stretch of coastline in Kuwait City over the course of 64 minutes. The intense show was part of the celebrations for the 50th anniversary of the nation's constitution. The elaborate spectacle broke a previous record set in Portugal in December, 2006, when pyrotechnics experts set off some 66,326 fireworks across 37 launch sites on the island of Madeira.

Lights before the booms

Light travels roughly a million times quicker than sound. For that reason, you often see lightning before you hear thunder, and fireworks, too, appear in the sky before you hear their explosions. With a little math, you can estimate how far you are from the action. Here's how: After you see a firework burst, count the seconds until the boom. Divide that number by three to get the distance, in kilometers, between you and the blast. So if the gap between seeing the firework burst and hearing it is 3 seconds, you are standing an estimated 1 kilometer (0.62 miles) away from the brilliant blast.

Big bucks for the bang

According to the American Pyrotechnics Association, the country bought 207.5 million lbs (93 million kg) of fireworks last year, spending $645 million. And a large chunk of the fireworks you'll see this week are foreign. The United States imported $227.3 million worth of fireworks in 2012, the vast majority ($218.2 million) from China, according to the U.S. Census Bureau. That's a fraction of the value of fireworks the United States exports: just $11.7 million in 2012.  

Waving a flag is a safer way to celebrate

Without fail, fireworks-related injuries spike around the Fourth of July in the United States. Between June 22 and July 22, 2012, more than 5,000 people ended up in the emergency room after being hurt by fireworks, most with burns to the hands, head or face, according to the U.S. Consumer Product Safety Commission (CPSC). Bottle rockets and sparklers, the favorites of children, were linked to at least one-fifth of those injuries. Besides harming people, fireworks can unsurprisingly cause fires -  and extensive property damage. In 2011 in the U. S., fireworks were behind an estimated 17,800 blazes resulting in about $32 million in damage, according to the National Fire Protection Association.

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