8. you and your friend, bill, are given a rock that you know has some silicon. you just learned that there are 3 common isotopes of silicon- silicon-28, silicon-29, and silicon-30. bill suggests that the rock might have equal parts of each isotope. what would be the average mass of silicon in the rock? show your calculations. how could you check to see if your ideas are correct?

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