NOTE: You need to have SP1 installed on Windows 7 in order to upgrade to Windows 10 using the Windows Update method shown in this video. If you are upgrading from Windows 8.1 some apps may not be supported yet on Windows 10.
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.
An example of an endothermic reaction is a first aid cold pack, in which the reaction of two chemicals, or dissolving of one in another, requires calories from the surroundings, and the reaction cools the pouch and surroundings by absorbing heat from them.n exothermic chemical reactions, the heat that is released by the reaction takes the form of electromagnetic energy. The transition of electrons from one quantum energy level to another causes light to be released.