The nucleus is the cell as

A nucleus is an organelle found in the eukaryotic cells. Inside it's fully enclosed nuclear membrane, it contains the minority of the cell's genetic material. This material would be called DNA molecules.

Hope this helps! If not I'm so sorry. Have a lovely day

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.

thats how its supposed to be