Which of these statements about Earths crust is true A:it includes the continents and ocean floor B: it includes the continents and the ocean floor. C:it is a changing moving surface with the same thickness everywhere. D: it is a layer of solid rock that remains the same throughout the time

explanation:

0.07 g/cm³

1.37 g/cm³

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.