Why is earth nicknamed the “blue planet”? a. the global oceans have tinged the land with a blue color. b. nearly 71 percent of its surface is covered by oceans. c. ocean waters reflect in the sun light, lending a blue hue. d. the continents appear dark blue in satellite photographs.

The Earth is nicknamed as a 'Blue Planet' because nearly 71 percent of its surface is covered by oceans.

Explanation:

The Earth is covered by a unibody made up of oceans which span 71% of the Earth's total surface area. These oceans appear dark blue in color when viewed from the space. The depth of the oceans and the scattering of light are the factors responsible to make the oceans appear blue. Thus, it is because of the dominance of the blue colored oceans on the 'surface of the Earth', the Earth is nicknamed as a blue planet.

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