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You answer your own question. There is a fall in temperature because the reaction is endothermic. The reaction needs energy, so unless you can supply some heat, the temperature will fall. Eventually, some heat from the surroundings will transfer and equilibrate the temperature. Temperature of the system is a measure of the global energy. Most reactions are exothermic so now the temperature rises and then transfers to the surroundings. A very famous example is a burning fire.
Aug 26, 2015. Because they require energy. An endothermic process is one that needs to have energy added in order to take place. A simple example of an endothermic process is the melting of ice, because ice doesn't melt unless you put energy into it. This is also the case with other phase changes. If we want to boil water, we need to heat it up by pumping energy into it, and then once it boils we need to continue pumping energy into it until it has all turned to steam. However... Not all phase changes are endothermic.