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.
Exothermic and endothermic reactions. In some reactions, the energy that must be absorbed to break the bonds in the reactants, is less than the energy that is released when the new bonds of the products are formed.This means that in the overall reaction, energy is released as either heat or light.This type of reaction is called an exothermic reaction.xothermic and endothermic reactions. In some reactions, the energy that must be absorbed to break the bonds in the reactants, is less than the energy that is released when the new bonds of the products are formed.