Which statement is true about this reaction 14/7n + 1/1h > 15/8o A. it is a practical source of energy on earth
B. it occurs only outside the solar system
C. its product is heavier than each of its reactants
D. it shows the critical mass of an element

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.