PYROTECHNIC

How they work:

A) What components make up a firework

B) How a firework produces lights and sparkles

C) Fireworks at an atomic level

D) Pyrotechnics vs. fireworks

E) What is a flash point

Short movie of explaining how fireworks work! (click on Anatomy of fireworks requires flash)

A) Here below is a basic wavelength range 6 basic colors

Colors          Emitters used                      Wavelength range


Yellow          Sodium D-line atomic emission 	    589 nm

Orange          CaCl, molecular bands               several bands, 591-
                                                    599 nm, 603-608 nm
                                                    being the most intense

Red	        SrCl, molecular bands	            a: 617-623 nm 
                                                    b: 627-635 nm
                                                    c: 640-646 nm

Red	        SrOH(?), molecular bands	    600-613 nm

Green	        BaCl, molecular bands	            a: 511-515 nm
                                                    b: 524-528 nm
                                                    d: 530-533 nm

Blue	        CuCl, molecular bands	            403-456 nm,
                                                    several intense
                                                    bands, less intense
                                                    bands between 460 nm
                                                    and 530 nm

B) Light production and sparkles                 Interactive Fireworks Display (VERY FUN!!!!!!!)

 Fireworks consist of a pyrotechnic mixture which is simply any combination of substances (elements or compounds) added with heat to produce a reaction (example: potassium nitrate, charcoal, and sulfur = gunpowder).  Now this mixture is stable at room temperature it is only until heat is added that the mixture breaks down its chemical bonds and forms a new compound. The energy that is left over after the new compound is formed is released as heat. 

Fireworks produce light three ways: incandescence, atomic emission, and molecular emission.  Incandescence is similar burners on an electric stove. When these substances get hot they shed some of their excess energy as visible light. The hotter it is the brighter it glows. Atomic emission is when atoms or molecules of various substances are heated they are briefly boasted to an excited state and when they return to there normal state they emit light of a specific wavelength (example: sodium-vapor street lights). Molecular emission is similar to atomic emission except the process is done with compounds rather than pure elements. 

Different elements added to a pyrotechnic mixture create different reactions.  For example: a mixture of of potassium, perchlorate (an oxidizer) and fine aluminum or magnesium powder create a flash of bright white light and because it burns very quickly, a loud boom ( this "boom" is caused by expanding gasses colliding with the surrounding air.)  In fireworks this is called "flash-and-sound" powder.

Larger metal particles retain heat longer then powders and can continue to burn after the oxidizer is gone by drawing oxygen from the air. As a result, they create white sparks rather than a flash of light.  The larger the particles of metal the longer the sparks last. 

Now we will get into the casings of fireworks or "shells".  There are two types of basic shells, American-European style and Japanese-style.  American-European style shells are typically cylinders seven to thirty inches in diameter.  They are launched from metal, plastic, or cardboard mortar tubes.  At the bottom of these shells is a portion of black powder.  When it's ignited, the hot gases it produces fill the tube and send the shell flying a few hundred of meters into the air. At the same time a time-delay fuse is ignited. When the shell is far above ground, this fuse sets off another black-powder charge (called a bursting charge) that breaks open the shell and ignites the metal or color-composition pellets (stars) which are packed into the shell.  These pellets (stars) are expelled outward in a random pattern of color and light.   Japanese-style shells are spherical instead of cylindrical and the pellets are arranged around the central black powder bursting charge. This setup creates a symmetrical pattern when the shell explodes.  Stars may just flash and sparkle or produce extended trails, depending on their composition.  Some compositions don't produce much heat and light, but do produce a lot of gas.  A composition that produces an abundance of gas pressed into a narrow tube creates a whistling sound as the shell descends. 

Here is a list of which compounds create different colors:

C.    How are Fireworks and Light Related to Atomic Structure?

Energy is supplied to fireworks causing an explosion or chemical change that vaporizes the atoms or molecules and the electrons move to an excited energy state.  As electrons move to their ground state, their extra energy as light corresponds to one or more specific wavelengths of visible light.

Bohr Model (1913)

·         Bohr said that electrons emit light as they move from an excited state to their ground state.

·         The ground state of an electron is the state of lowest possible energy.

5 colors that are of basic use in all fireworks are:

  Because the energy level are found in the Balmer series this means that the final energy level of all compounds is = 2.

D) Here is a short description of pyrotechnics vs. fireworks.

     As stated by Petri Pihko:   The word pyrotechnics refers to the art, craft and science of fireworks. As such, it is related to a variety of arts and sciences - as an underdeveloped art, it is nevertheless comparable to many other human arts, such as music, theatre and film; as a science, it attempts to understand and quantify the chemical and physical phenomena that characterizes pyrotechnic reactions. As a craft and art, pyrotechnics originated around 1st century AD in China, with the invention of black powder. As a science, however, pyrotechnics is quite young. The basic phenomena of flame and color production are now well established, but novel effects and novel materials still continue to be discovered.

Fireworks are the physical products of pyrotechnics. In simple terms pyrotechnics is the creation of fireworks amongst other aspects.   

E) Flash point: The Flash Point of a chemical is the lowest temperature at which a flame will propagate through the vapor of a combustible material to the liquid surface. It is determined by the vapor pressure of the liquid, since only when a sufficiently high vapor concentration is reached, can it support combustion. It should be noted that the source of ignition need not be an open flame, but could equally be, for example, the surface of a hot plate, or a steam pipe.

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LINKS

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How do lasers work!

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