The density of iron is 7.87 g/ml. what is the mass of a 4.00 cm × 4.00 cm × 1.00 cm block of iron?

Find the volume of the block : V = L x W x H 
find the volume of the block : V = 4.00 x 4.00 x 1.00 = 16.00cm3

A cm3 is = to a ml

so the block has 16ml of iron so now to find its mass : M = D x V

Mass = 7.87 x 16 = 125.92g or 126g if rounded 

hope that helps 

I’m not sure what your trying to say here.. can you clarify again?

The mass has escaped into a gas which you can not see so the law stays true.