Atomic masses are usually expressed as averages due to the existence of what phenomenon?

Ammonium perchlorate nh4clo4 is the solid rocket fuel used by the u.s. space shuttle. it reacts with itself to produce nitrogen gas n2 , chlorine gas cl2 , oxygen gas o2 , water h2o , and a great deal of energy. what mass of nitrogen gas is produced by the reaction of 2.1g of ammonium perchlorate?

What happens to the temperature of a substance when the average kinetic energy of its particles increases?

Which substance—wood or silver—is the better thermal conductor? a thermal conductor is a material that requires very little heat energy to change its temperature. explain your answer.