Identify substances A, B, C, and D as a solid, a liquid, or a gas by placing a letter in each of the small circles below. In the larger circles, draw models of the particles of each substance.

a. decomposes use carbon from dead organisms as fuel for cellular respiration, returning carbon dioxide back into the atmosphere.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.

genetic variation will increase because of a new habitat and food source.

explanation: