The density wave theory suggests that the spiral arms of the milky way galaxy are the result of a wave moving around the galaxy.

The density wave theory suggests that the spiral arms of the Milky Way Galaxy are the result of a Spiral Density Wave moving around the Galaxy.

Place the point of the compass on point b and draw an arc that intersects  be¯¯¯¯¯  , using    ab    as the width for the opening of the compass.  hope it

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