Two colorless chemicals combine inside a glow stick. When the chemicals combine, they produce
brightly colored light. The glow stick's temperature
does not change.
emission of heat
emission of light
color change
formation of gas

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.