Copper is made of two isotopes. copper-63 is 69.17% abundant and it has a mass of 62.9296 amu. copper-65 is 30.83% abundant and it has a mass of 64.9278 amu. what is the weighted average of these two isotopes?

To find the average mass of an element you add the mass of each isotope multiplied by it's relative abundance.

[(mass of Cu⁶³)x(relative abundance of Cu⁶³)] + [(mas of Cu⁶⁵)x(relative abundance of Cu⁶⁵0)]= average mass of Cu

[(62.9296)x(.6917)] + [(64.9278)x(.3083)] = 63.54amu

it should have an internal chamber and two thermometers sticking out of the top. the internal chamber will also be closed off from the outside.