Calculate the entropy change (a) of water, (b) of all other bodies, when 1 mol of supercooled water freezes at -10 oc and 1 atm. take the heat capacity of water and ice as constant at 75 and 38 j k-1mol-1respectively and the latent heat of fusion at 0oc as 6026 j mol-1.

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.

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".