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Re: Flame Tests

Submitted by jellis on Sun, 02/21/2010 - 15:28

Okay so we just finished up this lab in chem class on friday and we have to do post lab questions. So heres the question: Some substances you tested produced a color in the flame of the bunsen burner. What is happening in the atom to produce this colored flame? How could this color be used to identify the element? What are some pracical applications of this knowlege?

so the substances were sucrose which melted, paraffin which melted, calcium chloride which truned the flame reddish pink, sodium sulfate which turned the flame yellow/orange, iron which had orange sparks, aluminum pellet which did nothing and copper II sulfate which turned the flame green and blue.

help please!


jellis wrote:

Okay so we just finished up this lab in chem class on friday and we have to do post lab questions. So heres the question: Some substances you tested produced a color in the flame of the bunsen burner. What is happening in the atom to produce this colored flame? How could this color be used to identify the element? What are some pracical applications of this knowlege?

Perhaps reading through this well explained page will help.

http://www.chemguide.co.uk/inorganic/group1/flametests.html

so the substances were sucrose which melted, paraffin which melted, calcium chloride which truned the flame reddish pink, sodium sulfate which turned the flame yellow/orange, iron which had orange sparks, aluminum pellet which did nothing and copper II sulfate which turned the flame green and blue.

help please!


wow. thats so cool. thank you. how did you find that?


jellis wrote:

wow. thats so cool. thank you. how did you find that?

chemguide.co.uk is a popular site for chemistry students here in the uk(it covers up to a first year level undergraduate here), which might or might not be different from the one in us


wow. okay cool. thanks for showing me that. i greatly appreciate it.


In my chem class we just got done not too long ago with a flame test lab.  We took the liquid forms of several elements or solutions and put them in a flame to see what color the flame would turn.  In an atom when electrons go from their ground state to an excited state they gather energy in the form of photons.  When the element goes from the excited state back to the ground state it releases the photons which turn into what our eyes see as color.  Heat (as in the flame) is one way to excite an electron.  In your test some of the electrons got excited and some didn't. (This is based on the fact that you said some melted)  The color of the flame depends upon the amount of energy the electron picked up when it got excited.  The higher/longer the wavelength is the brighter the color.  The highest/longest wavelength produces a red flame while the lowest/shortest produces violet. 
This can be applied to neon lighting signs in the real world.  Different elements added to the neon will change the colors of the gas inside the lighting tube.  You can see red, blue, yellow, pink, and many other colors. 
Based on the name or what it was named for you can sometimes predict the element's flame color.  Rubidium's flame is probably gonna be red, based on the 'ruby' part of its name. Cesium was named for its sky blue spectral lines so you could guess its flame is probably going to be blue.
Again I hope this helps.


Smiles wrote:

In your test some of the electrons got excited and some didn't. (This is based on the fact that you said some melted) 

This was one of the amazing discovery that earns Albert Einstein a nobel prize. The absorption or emission of a photon can only occur if the energy separation between two energy level(ground and say the first excited state) equals a quanta of energy, ie it is quantized. If the energy supplie(E=hc/wavelength where h is planck constant) is not equal to this energy separation gap, then no transition can occur. Just an extra knowledge for you!