When is mechanical energy NOT conserved? Question 4 options:

When the electricity is turned off

When it is cold outside

When you are in outer space

When there is significant friction or air resistance or other force affecting on the object.

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.