Organic molecules are sometimes found within meteorites that crash into earth. which meteorite condition in space is similar to what most likely was present on early earth?
abundance of oxygen
very cold temperatures
presence of inorganic molecules
low levels of ultraviolet radiation

The early earth had all the three conditions except abundance of oxygen. The  atmosphere of the early earth was same as that of the condition present in space. The organic molecules found in the meteorites might have originated from the inorganic substance that is present in the space that was present in meteorite. The early earth had very low amount of oxygen and very cold temperature, presence of inorganic molecules and low levels of ultraviolet radiation.

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.