Which balanced equation represents a chemical change?
(1) h2o(l) + energy → h2o(g)
(2) 2h2o(l) + energy → 2h2(g) + o2(g)
(3) h2o(l) → h2o(s) + energy
(4) h2o(g) → h2o(l) + energy

The answer is B because energy was added to 2H2O in order to produce a chemical change of 2H2 and 02 seperately.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.