Describe the motion of molecules in these two substances when the ice cube is placed on the
radiator.

When in direct contact, the fast-moving molecules in the radiator collide with the slow-moving molecules in the ice cube. Kinetic energy is transferred from the molecules in the radiator to the molecules in the ice cube, causing a slowdown of the radiator molecules and an acceleration of the ice molecules.

Explanation:

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.