Name two other methods through which the primary data can be collected apart from direct personal investigation.

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

Why the planet stays in orbit is because of inertia (object stays in motion until a force changes it’s motion) also the atmosphere and gravity!

According to new research, more than 5..5 million deaths are associated with polluted air. hope this : ).

Because ours has not callosped, its working without the planets crashing into eachother, and the sun is the right distance away.