GMAS 5th Grade Science Practice Test

Matter is made of tiny building blocks called atoms. An atom is the smallest unit that still represents the element it comes from, so it’s the basic piece used to describe what substances are made of. Inside an atom, a center called the nucleus contains protons and neutrons, with electrons nearby in surrounding space. This idea fits the statement that atoms are the smallest unit of matter, because atoms are the fundamental pieces that everything is built from. The other options describe much larger levels of organization, a molecule (which is two or more atoms bonded together), or a tool used to measure weight, which isn’t what matter is made of.