How do you identify whether a solution is a buffer solution or not

You check whether the PH level changes when you add little amounts of strong acid or base. If you see that there is little to no change in the PH, then it is a buffer solution.

Hope that answers your question

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.