Which of the following is/are a true statement about 1 mole samples of oxygen,
hydrogen, and nitrogen gas at STP?

I. Only oxygen and hydrogen are diatomic molecules.
II. All 3 samples occupy the same volume.
III. All 3 samples have the same mass.

A) I only
B) II only
C) I and II only
D) II and III only
E) I, II and III

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.

i don,t know so just answer mine