How would you describe the appearance of the substance before the phase change?

Melting -The substance changes back from the solid to the liquid Condensation-the substance changes from a gas to a liquid

Melting: the substance changes back from the solid to the liquid. Condensation: the substance changes from a gas to a liquid. Vaporization: the substance changes from a liquid to a gas. Sublimation: the substance changes directly from a solid to a gas without going through the liquid phase.

Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which increases the substance's temperature to the melting point.

Explanation:

A) fluorine. It is the most reactive of all molecules and diatomic. The density pattern of the periodic table follows a higher density to the left and down. Lower density elements are more to the right and up.