What important scientific survey did the HMS Challenger undertake in 1872? How did they measure the depths of the ocean waters in that time period?

They immigrated for religious freedom

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen

Answer after wwii, communist countries in eastern europe formed the warsaw pack, a military alliance, and comecon, an economic alliance;

Answer erosion,oil spills,pollution,tourism,urban development;