sumo#pure_substance  substances with constant composition, e.g., table salt, sugar, water, iron, copper and oxygen
  closed_exclusion:  mixture
  supertype:  substance__amount_of_matter___divisible_entity_without_discrete_parts  object in which every part is similar to every other in every relevant respect; more precisely, something is a substance when it has only arbitrary pieces as parts - any part has properties which are similar to those of the whole; note that a substance may nonetheless have physical properties that vary, e.g., the temperature, chemical constitution, density, etc. may change from one part to another; examples: body of water, air, cement
  subtype:  compound_substance  substances that contain two or more elements (sumo#elemental_substances), in definite proportion by weight; the composition of a pure compound will be invariant, regardless of the method of preparation; compounds are composed of more than one kind of atom (element); the term molecule is often used for the smallest unit of a compound that still retains all of the properties of the compound; examples: table salt (sodium chloride, NaCl), sugar (sucrose, C_{12}H_{22}O_{11}), and water (H_2O)
  subtype:  elemental_substance  pure_substances that cannot be separated into two or more substances by ordinary chemical (or physical) means; this excludes nuclear reactions; elemental_substances are composed of only one kind of atom, e.g., iron (Fe), copper (Cu), and oxygen (O_2); elemental_substances are the simplest pure_substances
     subtype:  metal  an elemental_substance that conducts heat and electricity, is shiny and reflects many colors of light, and can be hammered into sheets or drawn into wire; about 80% of the known chemical elements (sumo#elemental_substances) are metals
     subtype:  atom  an extremely small unit of matter that retains its identity in Chemical reactions; it consists of an atomic_nucleus and electrons surrounding the atomic_nucleus
     subtype:  subatomic_particle__subatomicparticle  the class of elemental_substances that are smaller than atoms and compose atoms
        subtype:  atomic_nucleus  the core of the atom; it is composed of protons and neutrons
        subtype:  electron  sumo#subatomic_particles that surround the atomic_nucleus; they have a negative charge
        subtype:  proton  components of the atomic_nucleus; they have a positive charge
        subtype:  neutron  components of the atomic_nucleus; they have no charge

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