The smallest unit of a substance that has the properties would be either an atom, or more probably a molecule. An atom does not ordinarily exist by itself in nature.
The smallest unit of a pure substance that consists of two or more atoms held together by a chemical bond is a molecule.
A molecule
An atom is the smallest particle possible of a pure substance. A molecule is the smallest possible particle of a compound.
compound
This is called a compound.
into smallest partical
Molecule, or atom in the case of a pure elemental substance.
The smallest unit of a pure substance that consists of two or more atoms held together by a chemical bond is a molecule.
A single hydrogen atom.
A molecule
An atom is the smallest particle possible of a pure substance. A molecule is the smallest possible particle of a compound.
two or more substances that are together that are together but do not combine to form a new, pure substance
an atom is the smallest unit of an element, but an element is a pure substance
Compound
compound
If the pure substance is not an element, the smallest part is a molecule (which is made of atoms) for instance, pure water is made of water molecules, which are made of 2 hydrogen atoms and 1 oxygen atom If the pure substance is an element, the smallest part is an atom. (which is made of Protons, Neutrons, and Electrons) Pure hydrogen is made of atoms. A stable hydrogen atom has 1 proton, 1 neutron, and 1 electron. Protons and Neutrons can be broken down further into Quarks, Leptons, and Bosons. The Electron is a type of Lepton.
Density is specific for each substance. Also the measurement is generally simple.