O que acontece quando uma moeda escurece? (oxidos quimica )

As moedas ficam sujas devido ao oxigênio do ar reagindo com o metal para formar óxido de cobre. Eles se tornam mais escuros à medida que envelhecem, à medida que a camada de óxido aumenta. O vinagre é um ácido (ácido acético) que pode ser usado para limpar superfícies e remover os óxidos indesejados.

Explanation:

The substance is a metal, mainly iron or copper.

Metals are classified as those elements which have a strong structure, hard, malleable, ductile, sonorous and have high heat and electricity conductivity.

Metals are not soluble in water in atomic state because they are in crystal forms which are very hard to be broken by water.

They are conductor for both heat and electricity. Metals have free electrons in their outermost shell which can be free in the lattice which helps to conduct electricity even in molten state.

And metals do usually have very high melting points. So they aren't easy to melt at all. Main conductors that are used are iron and copper.