Any atom or molecule with a net charge, either positive or negative, is known as an_​

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

Tropical climate is experienced in the nothern countries of south america

The correct answer is:   [b]:   "physical systems" .