Final answer:
The color of heated iron changes due to blackbody radiation, with hotter temperatures causing the emitted light to shift from longer wavelengths (red) to shorter wavelengths (blue or white) according to Wien's Law. Initially, at lower temperatures, only infrared radiation is emitted, but as the temperature rises, the visible spectrum is reached, starting with red and continuing through orange, yellow, and finally white as it gets hotter.
Step-by-step explanation:
The change in colors observed as a piece of iron is heated is due to the phenomenon of blackbody radiation, which is explained through physics. As the temperature of an object increases, the molecules that make up the object move more rapidly and collide with each other, resulting in higher kinetic energy. This energy is then released in the form of electromagnetic radiation, which includes visible light. The color of the light is dependent on the temperature of the object due to Wien's Law, which states that hotter objects emit light at shorter wavelengths. As the temperature rises from low to high, the dominant wavelength shifts from the longer wavelengths (red) to shorter wavelengths (blue).
At a lower temperature, an object may emit infrared radiation, which does not produce visible light. As the temperature increases, the radiated light enters the visible spectrum, starting at red. This is followed by orange, yellow, and white as the object becomes hotter and the dominant wavelength moves into these respective colors. The intensity and color of thermal radiation emitted by a hot object therefore change as the temperature increases.