When a solid melts, why does it absorb energy?

Does anyone know a lot about how to: - calculate mass of magnesium metal - calculate the actual yield of magnesium oxide - calculate the theoretical yield of mgo - calculate the percent yield of mgo - determine the percent yield of mgo - determine the average percent yield of mgo i had to do an online lab and its asking these questions but i have no idea where to start or how to be able to find these things. i can post the chart of the data from the lab or if you can tell me exactly how i can find each.

May someone me with these science questions

Amap that uses a range of colors and shading to represent the elevation, depth, or landscape of specific features on earth is a/an map.