To prevent the pollution of groundwater, waste water collected from landfills should be a. diluted by mixing it with drinking water. b. filtered by soil and plants. c. piped to nearby lakes and streams. d. treated before it is released.

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.