Describe the different layers of earths interior.

The Earth's interior consists of rock and metal. It is made up of four main layers: 
1) the inner core: a solid metal core made up of nickel and iron (2440 km diameter) 
2) the outer core: a liquid molten core of nickel and iron 
3) the mantle: dense and mostly solid silicate rock 
4) the crust: thin silicate rock material

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