Consider the following reactions. (note: (s) = solid, (l) = liquid, and (g) = gas.)
mg(s) + ½o2(g) → mgo(s) + 146 kcal/mole
h2(g) + ½o2(g) → h2o(g), δh = -57.82 kcal/mole
the temperature of the surroundings will:

increase
decrease