A roller coaster is at the top of a 72 m hill and weighs 966 N. The coaster (at this moment) has energy. Calculate it.

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

colorless gas, exhibiting a blue glow when placed in an electric field

b) solid

its a type of rock