Why do reactions need to be balanced? A. Because the reactants must be the exact same as the products

B. Because of the conservation of energy

C. Because the volume of reactants must equal the volume of
products

D. Because atoms are not lost or gained in a chemical reaction

A part.

Explanation:

Because the reactants must be the exact same as the the products.

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.

the answer is 75.0%.