An iron nail (fe) is placed into a solution of copper(ii) sulfate (cuso4). after some time, the blue color of the copper (ii) sulfate disappears and some copper-colored solid (cu) is found on the surface of the nail. the solution now contains iron (ii) sulfate (feso4), and the container feels warmer than before the reaction.. 1. does this reaction absorb or release absorb or release energy? how do you know? . 2. what do the color changes indicate?

The reaction is a displacement reaction. Iron is more reactive than copper. Hence, it displaces copper,forming iron II sulfate and copper metal. 
This reaction is an exothermic reaction, hence it releases energy. The colour change indicates that iron has displaced copper. 

This reaction shows that iron is more reactive than copper as it displaces copper from its solution and iron passes into solution as Fe2+ ions and ferrous sulfate solution is formed. It is called a single displacement reaction. There is a release of energy since the container feels warmer. This type of reaction is called exothermic. The color changes indicate that there is a chemical reaction that occurred. The copper from the solution will now be deposited on the nail.

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom. 

Its the second one nonmetals are moldable and easily shaped