How has Charles Darwin contributed to the study of evolution? A.
He proposed the theory of natural selection.
B.
He excavated and studied fossils.
C.
He was the first one to use a 3-D printer.
D.
He proposed the genetic relationship between species.

Different isotopes indicate that an element will have different numbers of

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?

Some liquids can be distilled, but only at temperatures that are so high that it is impractical, or so high the compound decomposes. explain why distillation such compounds at significantly less than atmospheric pressure (some degree of vacuum) would solve this problem.