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.
1 The nearby Clearwater Cave System is believed to be the world's largest cave by volume, with a calculated volume of 30,347,540 m 3 (1.071713 Ã 10 9 cu ft). 2  The largest passage ever discovered is in the Son Doong Cave in Phong Nha-Káº» Bang BÃ ng National park In Quáº£ng Binh, BÃ¬nh.  province vietnam The cave system with the greatest total length of surveyed passage is Mammoth Cave in Kentucky, USA, at 643 km (400 mi). 2  This record is unlikely to be surpassed in the near future, as the next most extensive known cave is Jewel Cave near Custer, South Dakota, USA, at 267 km (166 mi).