What observation could be evidence that a chemical reaction has occurred?

Asample of sea water contains 6.28g of sodium chloride per litre of solution. how many milligrams of sodium chloride would be contained in 15.0ml of this solution?

Four statements about the development of the atomic model are shown below. a: electrons have wavelike properties. b: atoms have small, negatively charged particles. c. the center of an atom is a small, dense nucleus. d: atoms are hard, indivisible spheres. which order of statements represents the historical development of the atomic model? c-d-a-b c-d-b-a d— в-а — с d-b-c-a

Sheela and her brother hari were sitting in the living room, watching tv. suddenly hari said that he thinks something is burning in the other room. how did he get the burning smell?