Look at P, Q, R

1. one is very cold with long dark winters, which one?

2. one is hot and wet all year and still has some tropical rainfall, which one?

3. explain your reasoning for each

The answer to this question is b

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