In order to construct a valid criticism, it is important to a come up with a list of your opinions on the subject
b. get the opinion of a peer on the subject
C. research data on the subject, and analyze it for reliability
d. consider only one factor that may contribute to a possible outcome

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.