What happens to the log if the density of water is decreased?
a. the log sinks in the water
c. the log rises out of the water
b. the log rises in the water
d. nothing change

A. the log sinks in the water as buoyant force is a function of density.

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