Mr. McPhillip has a ribbon of magnesium (Mg), a silvery metal. As a demonstration for his class, he sets the metal on fire. It burns brightly, leaving behind a whitish powder. The magnesium is
and the powder produced by burning it is

the answer is minerals.

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.