A $100 \mathrm{~g}$ piece of iron has twice the volume as a $50 \mathrm{~g}$ piece of iron. True False

Step 1 ：The density of a material is defined as its mass per unit volume. If the two pieces of iron are of the same material, they should have the same density. Therefore, a piece of iron that is twice the mass should also be twice the volume.

Step 2 ：So, the statement is true.

Step 3 ：Final Answer: \(\boxed{True}\)