Forming a chemical bond releases energy and therefore is an exothermic process. Exothermic reactions usually feel hot because it is giving heat to you. Endothermic-a process or reaction that absorbs energy in the form of heat. Breaking a chemical bond requires energy and therefore is Endothermic.
karma level 71199. The Seikan Tunnel is a 53.85 km (33.46 mi) railway tunnel in Japan, with a 23.3-kilometre (14.5 mi) long portion under the seabed. Track level is about 140-metre (460 ft) below seabed and 240-metre (790 ft) below sea level. It is the longest undersea tunnel in the world, although the Channel Tunnel between the United Kingdom and France has a longer under-sea portion.
Two kilometers under the Alps, workers are finishing the longest, deepest railway tunnel in the world. When the Welsh chronicler Adam of Usk traveled over Switzerland's wild and remote Gotthard Pass by oxcart on his way to Rome in 1402, he was so terrified that he asked his guides to blindfold him so he wouldn't have to look.