Chapter 17 Composition of Matter

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Chapter 17Composition of Matter

• Pure Substances
• Materials are made of a pure substance or a
  mixture of substances.

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• A pure substance is either an element or a
  compound.
• This means that the item cannot be broken down
  into simpler substances and still maintain the
  properties.

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Example

• An example of a pure substance is GOLD.
• If you take a piece of gold, you cannot break it
  down to something else. If you cut the gold in
  half, you will have 2 pieces of gold.

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Additional examples

• Helium (gas)
• Lead
• Platinum
• Oxygen

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Elements

• All substances are built from atoms.
• If all the atoms in a substance are alike, the
  substance is an element.
• Example The graphite in your pencil or the
  copper on a penny
• The graphite contains only carbon atoms and the
  penny will contain only copper atoms.

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Elements cont.

• There are 90 elements found in nature.
• More than 20 others have been made in
  laboratories, but most of them are unstable and
  last for only a short time.

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Examples of elements

• Mercury the silver liquid in a thermometer.
• The titanium in razor blades.
• The platinum in wedding rings.
• Gold not only used in coins but for spacecraft
  parts.

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Examples cont.

• Aluminum is used in blankets to retain body heat.
• Tungsten has the highest melting point for any
  metal. It is also very soft and easy to stretch.
• What is it used for?
• Light bulbs!

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More examples

• Lead has a high density, and is a good barrier
  for radiation.
• They sometimes place an apron over you when you
  have an X-ray.
• Americium is a component of a smoke detector. It
  is a radioactive metal that must be handled with
  care to avoid contact.

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Question?

• Where can you find a list of all the elements?
• The periodic table of course!!
• We will come back and spend a lot of time with
  this later.

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Compounds

• Compound two or more elements can combine to
  form a substance called compounds.
• A compound is a substance in which the atoms of
  two or more elements are combined.

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Compound Examples

• Example Water
• H2O contains hydrogen and oxygen.
• Chalk contains calcium, carbon, and oxygen.

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Dangerous compounds that we need to live.

• Salt contains sodium and chlorine.
• Sodium is a silvery metal that will explode
  violently when combined with water.

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• Chlorine is a greenish-yellow poisonous gas that
  is used in the gas chamber to execute prisoners.
• When you combine them You get a neutral Salt

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Mixtures

• A mixture is a substance that can be easily
  separated by physical means.
• Example Pizza toppings.

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Mixture Types

• There are 2 types
• 1) Heterogeneous Mixtures
• 2) Homogenous Mixtures