You are listening to a lecture. then the bell rings in the hallway. in order to hear this stimulus, neurons must carry electrochemical messages from your ears to your brain.

a. the production of carbon dioxide through the process of photosynthesis

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.