Chemistry – Matter

Matter is anything that has mass and occupies space – Solid, Liquid, and Gas. Mass is the measure of the amount of matter present.

Substance, Element, and Compound

  • Pure substance
    • A substance made up of only one type of atom or molecule (no contamination) – constant properties and composition (the same chemical formula)
    • Water (H2O), Salt (NaCl)
  • Element
    • A pure substance that cannot be broken down by ordinary chemical means (heating, add energy – electric current). A chemical formula for an element contains only 1 symbol. (O2, H2)
    • Atom: The smallest discrete particle of an element.
  • Chemical Compound
    • A pure substance that can be broken down by ordinary chemical means.
    • A chemical formula for a chemical compound contains 2 or more element symbols. (H2O)
    • Molecule: The smallest discrete particle of a chemical compound. Atoms combine to form molecules.

2H2O (l) -> electric current -> 2H2 (g) + O2 (g)

  • Mixture
    • A random blending of 2 or more pure substances that do not react.
    • Homogeneous – a mixture that is chemically and physically consistent
    • Heterogeneous – a mixture that is no chemically and physically the same throughout

Properties

  • Physical properties are based on observation or measurement with no change in the composition of matter.
    • color, melting point
  • Chemical properties are based on the reactivity of matter with a change in composition.
    • chemical change
    • iron rust: 2Fe (s) + O2 (g) + H2O (l) -> Fe2O3 (s) + H2 (g)
  • Intensive properties do not depend on the amount of matter present.
    • color, density, boiling point
    • Chemical properties are always intensive properties.
  • Extensive properties DO depend on the amount of matter present.
    • mass, volume

  • Law: Observations in nature to which there are no exceptions.
  • Law of Mass Conservation
    • In a chemical reaction, mass is neither created or destroyed.


  • A Measurement is a quantitative observation that is represented with a number and a unit.

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