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

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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

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• Law: Observations in nature to which there are no exceptions.

• Law of Mass Conservation
  • In a chemical reaction, mass is neither created or destroyed.

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