STATES OF MATTER The mass of an atom is determined by the number of protons and neutrons its nucleus contains. Protons and neutrons have about the same mass, 1.67 × 10⁻²⁷ kg. Define A = N + Z. Then if we have A kilograms of any material consisting of the same atoms, the number of atoms will be Avogadro's Number, 6 × 10²⁶.

Phase diagram for water.

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