When two substances are mixed and light is produced is it a chemical or physical change?

Why doesn't heat added to water make the tempature rise above 100c

Apump contains 0.5 l of air at 203 kpa. you draw back on the piston of the pump, expanding the volume until the pressure reads 50.8 kpa. what is the new volume of the air pump

If many scientists conduct the same or similar experiments, and all obtain similar results, a can be written, which is a generally agreed-upon statement that explains and predicts how a natural phenomenon works.