What type of noun is empty?

How can both Leonard Susskind and Steven Hawking be correct at the same time concerning energy loss or elimination in a Black Hole? What difference in densities caused the pattern of movement when the hot dye was placed in cold water? What is meant by phenotype plasticity in roots and shoots? What time of atom will always lose valence electrons to become an ion? How many oz of water in a gallon? Are children the most frequent victims of collisions between vehicles and pedestrians? What raw materials are used for making of carpets? Which colors are on the short side of the wave spectrum? The three elements of See What There is to See used to develop the skillful use of your eyes to become aware of all the important elements of the driving scene ar? What is the chemical formula of wintergreen oil? What decay decreases atomic mass by 1? Which direction does carbon dioxide move during internal respiration? What is an example venation leaf? What is a benzonitrile? Why do the roots of some aquatic plants become reduced or at times absent? Is remora a parasite? Can solar panels deliver a steady supply of power? What lanforms can isolate people? Is mineral oil food safe? What can you plant grass in besides fertilizer?