Imagine you live in Baltimore, Maryland which is 39 degrees north of the equator in the northern hemisphere. Which season are you experiencing at each point on the diagram and why?

Winter is D, spring is A, summer is B, fall is C

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