Black light
These are silver halides as AgCl and AgBr.
A photograph turns black in light negative. In a photographic negative, the areas that receive more light appear black when the negative is converted to a positive image.
A balck bird is not an element. No living thing is an element.
Bromine
Silver-based film stock turns black in a light negative, as it is developed using a chemical process that exposes the film to light and causes the silver halide crystals to darken where they have been exposed, creating the photographic image.
Bromine
Black chromate!
For example silver bromide or chloride.
Iridium is a metal that turns black when exposed to light and is used as a film coating for various applications, including optics and electronics.
It just stays black because when you mix black with anything it just turns black
the heating element turns black because it heats up all the water xxxx I think this is likely to be because your water supply is acidic (pH less than 7). This can dissolve the element over time. Probably best to replace the kettle with one with a concealed element.
A light bulb turns black when the filament inside it gets too hot and starts to burn, creating a layer of soot on the inside of the bulb.