The initial amount of low-quality energy available from an energy resource is called its net energy.

La cantidad de energía disponible de una fuente de energía determinada se denomina recurso energético. La escasez de recursos energéticos (petróleo, carbón y madera) en algunas de las fuentes de energía más utilizadas plantear necesidad de usar otras fuentes investigar el modo más rentable de emplearlas

Explanation:

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.