Chem failure

Example1:
'The reason iron rusts is that iron atoms will rust if exposed to damp air.' - True

Example2:
'Metals such as iron expand when heated because the atoms get bigger.' - False
A: Why false?
B: Because the atoms don't change right, so probably the kinetic energy increases... or, maybe they just, multiply.

HAHAHAH. Ohmygawddddd. diediedie