Why do chemical lab test change color during a reaction?

Answer 1

The answer is somewhat complex. In metal complexes, especially transition metal, crystal field theory and ligand field theory are useful. Basically depending on what the anion (ligand) is that binds to the metal it "splits" the energy levels of the d orbitals. Some ligands will cause greater splitting than others. Now a larger split causes a metal to absorb shorter wavelengths of light (higher energy) in the visible range and they will appear as Red, Orange type colors. This is because an element which absorbs short wavelength (eg blue light) emits the complementary color (eg yellow-orange). When the split is small the effect reverses. The spectrochemical series is a list of ions in order of strength of splitting.

Answer 2

because it has losted electrons, becoming an ion. THis is known as oxidation

Cu (s) -->Cu2+ + 2e-

Answer 3

A chemical lab test changes color during a reaction to see if the solution has reacted.

Answer 4

Colors represent the frequencies of the visible portion of the electromagnetic spectrum that are not absorbed by the substance in question.