What must be done to be certain that a chemical change has taken place?
a. check for the production of bubbles before and after the change.
b. demonstrate that a release of energy occurred after the change.
c. check the composition of the sample before and after the change.
d. demonstrate that energy was absorbed by the reactants after the change.

The image shows a sandstone formation with visible bands of different colors. what do the bands indicate about how this sedimentary rock was formed? choose two answers. a). the rock was made from more than one material. b). water was absent during the compaction and cementation process. c). sediments and other matter were deposited in layers before lithification. d). the rock was stretched horizontally by the pressure from surrounding rocks. e). layers of hot liquid in the rocks cooled and solidified at different tempatures