Which describes radioactive decay of a substance? 1) more of the radioactivity is lost during the first half-life than in later half-lives. 2) more of the radioactivity is lost during the fourth half-life than in the first half-life. 3) isotopes are the most stable during the first half-life. 4) isotopes are the least stable during the later half-lives.

1) More of the radioactivity is lost during the first half-life than in later half-lives.

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.

if you mean hydrogen and oxygen then water is the product