13. If ice did NOT float, the ecosystems
in bodies of water would due
to the body of water being frozen
throughout during freezing
temperatures.
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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

Answerweathering;

The answer is    d.  central highlands