Is a piece of obsidian a pure substance?

What is the pressure in a middle-latitude cyclone? Is CaCI2 eletrolyte? What did the temple of Saturn look like? What is main vent? Does the polarity be changed in an iontophoresis treatment? What are the building blocks of triglycerols? How can you determine an elements row on the periodic table? What is the measure of how quickly an asset can be converted to cash? What a song cycle? Do golden eagles hibernate or migrate? What is the leading cause of water contamination in countries without water treatment plants? What are countries in the interior plains? What does nitric oxide do for the body? What is geographical significance? Which is the best description of how the El Nino weather inversions impact global weather systems? What if only half of the water vapor that the air can hold is actually in the air.What is the relative humidity? The four subjects of the Quadrivium arithmetic geometry music and astronomy were thought of as the study of what and its relationship to physical space or time.? Is it true A highway overpass is a good place to hide from a tornado? When did Plymouth go to 12 volts? How old do you have to be to buy firework sparklers?