A Química por trás dos fogos de artifício!
Autor: Josafary Campelo, Gabriella Albuquerque | Publicado: 2012-12-13T21:07:00-08:00



Barra da Tijuca


O Fim do ano está bem próximo e na passagem de um ano para outro, cidades organizam shows com a beleza das várias cores dos fogos de artifício. Os fogos de artifício são materiais explosivos dotados de um pavio, para que nele se inicie a combustão. A energia gerada na reação de combustão faz com que os fogos de artifício subam e atinjam uma altura máxima. Ao chegar nessa altura, o excesso de energia é liberado sob forma de som e luz. É interessante notar que no momento da explosão, primeiro se ver a cor emitida pelo material para depois ouvir o estampido emitido por ele. Isso deve-se ao fato de a velocidade da luz ser maior que a velocidade do som, <!--[if gte mso 9]>
 
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<![endif]-->3.108
 m/s contra 340m/s . E essa luz de onde vem?


O recebimento de energia promove o elétron de nível.


Bom, os fogos de artifício são formados por uma mistura de pólvora e sais metálicos. A pólvora é responsável pela explosão e os sais metálicos são responsáveis pela cor da luminosidade emitida. A combustão provoca a promoção de elétrons para níveis de energia mais externos, que por sua vez, são mais energéticos. Porém, ao atingir a altura máxima, os elétrons que foram excitados, liberam a energia recebida em forma de luz, retornando aos níveis de energia de origem, sendo desta forma a quantidade de energia recebida igual a quantidade de energia emitida.&nbsp;

Certo. Mas existem várias cores para fogos de artifício. Como é isso?&nbsp;

As radiações são organizadas em um espectro eletromagnético de acordo 
com a frequência e o comprimento de onda emitido por elas. As cores 
ocupam uma região muito pequena do espectro a cor emitida pelos fogos de 
artificio vai depender do comprimento de onda emitido por ele e pode ser elucidada a partir da equação de Planck&nbsp; E= h.f, onde E é a energia do fóton; h é a constante de Planck e f a frequência da radiação. A partir do comprimento de onda, será determinada a cor do fogos de artifício. 


Espectro eletromagnético. A região do visível vai do comprimento de onda 400nm a 700 nm