Pure Substances, Elements, Compounds, and Mixtures

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Pure Substances, Elements, Compounds, and Mixtures
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What are pure substances?

• PURE SUBSTANCES ? Substances
• made of one kind of material with a
• unique set of chemical and physical
• properties. Elements and
• compounds are pure substances.

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What is an element?

• ELEMENT? a
• pure substance
• that cannot be
• broken down into
• simpler
• substances

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• There are slightly more than 100 known
• chemical elements that are arranged on the
• periodic table developed by Dimitri
• Mendelev. Each element is abbreviated
• with one or two symbols. The 1st letter is
• capitalized and the 2nd is not. Each symbol
• represents the English name, old name, or
• Latin name of the element.

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EXAMPLE

• (Latin) Aurum-Gold Au
• (English) Oxygen O
• (Old) Natrium Sodium - Na

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• Some elements are named after
• famous scientists, countries, states,
• and planets.
• (101) Mendelevium scientist
• (32) Germanium Germany
• (98) Californium California
• (92) Uranium - Uranus

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What are compounds?

• COMPOUNDS ? 2 or more elements
• chemically combined
• EX magnesium oxide (MgO2)
• Magnesium Oxygen

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Separating Compounds

• Compounds can be separated by chemical
• means because they are chemically
• combined. Compounds can be broken down
• by electrolysis. Electrolysis literally means
• to tear apart with electricity. It is a
• technique using an electric current to pass
• through a substance. If the substance is a
• compound, it may be broken down into the
• separate elements that form it.

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EX H2O (water)

• If an electric current passes through
• the compound, the compound will
• break down into the two elements
• hydrogen and oxygen.

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What is a mixture?

• MIXTURES ? a blend of two or more
• pure substances

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Types of Mixtures

• Heterogeneous Mixture ? a mixture that has
  visibly different parts
• Homogeneous Mixture ? mixtures that do not
  contain visibly different parts
• (Hetero- and Homo- are two Greek roots that
• mean different and same.)

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Heterogeneous vs Homogeneous
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Separating Mixtures

• Mixtures can be separated by
• decantation, filtration, crystallization,
• distillation, chromatography.

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Decantation

• Decantation ? gentle pouring off of a liquid
  without disturbing a solid sediment
• EXAMPLE
• cleaning a fish tank and leaving behind most of
  the sand, shells, and plants
• drinking coffee and leaving small residue of
  coffee grounds behind in a cup

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Filtration

• Filtration ? passage
• of a liquid or gas
• through a porous
• substance for the
• purpose of removing
• suspended solids.
• A mixture of water
• and an insoluble
• substance like sand
• can be separated by
• filtering.

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Crystallization

• Crystallization refers to the formation of solid
  crystals from a homogeneous solution. It is
  essentially used as a solid-liquid separation
  technique.

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Distillation

• Distillation ? the process in which a liquid is
  evaporated and the vapors condensed

• The solution is heated until it boils. The liquid
  with the lowest boiling point boils first and
  becomes a vapor (gas). The vapor is cooled in the
  condenser until the temperature falls below the
  boiling point when it condenses back into a
  liquidwhich is collected in a container.

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Chromatography

• Chromatography ? process used to separate
  mixtures using a solvent (water) that carries a
  solute (ink) up a strip of paper

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• Heterogeneous mixtures can be separated by
  physical means such as filtration.
• Homogeneous mixtures can be separated by
  distillation, crystallization, chromatography.