I NEEDED HELP
on key concept

My results provide evidence of variations within the classroom since everyone's results do vary and show different lengths. On top of that, the results show the diversity between the class and it represents the difference of the measurments thorughout the classroom population.

I don’t exactly know what you mean, but I think on the key concept it is trying to tell you to find your classmates forearm length and find the average of the class, and then see how your arm length varies to your classmates.

what's the

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.