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Classification of Matter Classification of Matter Chapter 17 p 517 541

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									Classification of Matter

       Chapter 17
       p. 517-541
Composition of Matter

      Chapter 17
       Section 1
      p. 518-525
          Pure Substances
• Have you ever looked at a picture and
  couldn’t tell whether it was a painting or
  copy? Did you go up and touch it?
• The properties of materials can be used to
  classify them into categories.
          Pure Substances



• Materials are either pure substances or a
  mixture of substances.
• Pure substances – AKA substance – are
  either an element or compound
            Pure Substances
• Substances can’t be broken down into
  simpler substances and still have the
  same properties
• Ie – what are the properties of a piece of
  gum?
• If I break it into smaller pieces, does it still
  have those properties?
• Ie – what are the properties of water?
• If I separate a bottle of water into different
  glasses, is it still water?
                 Elements
• Remember:
  – An atom is the smallest piece of
    matter that still retains the
    properties of the element.
• All substances are made from
  atoms.
• If all the atoms in a substance
  are alike, it is called an element.
                 Elements
• Ie – the graphite in your pencil is an
  example of an element.
  – All the atoms in the graphite are carbon atoms
• Ie – the copper covering on your penny is
  an example of an element.
  – All the atoms that make up the covering are
    copper atoms.
• Ie – the zinc in the middle of your penny is
  an example of an element.
  – All the atoms that make up your penny center
    are made of the element zinc.
                 Elements
• There are 90 elements found in nature
• Over 20 have been made in laboratories
  – These are usually unstable and don’t last long

  •Some elements you might recognize
  in your everyday life.



                      Copper pot or pan
               Compounds
• Two or more elements can combine to form a
  compound
• These elements combine in a fixed proportion
• Ie - water is a compound in which 2 hydrogen
  atoms combine with 1 oxygen atom
• Can you imagine putting a silvery metal and a
  greenish-yellow, poisonous gas on your food??
              Compounds
• You may have if you dashed some salt on
  your food today!
• Salt is a compound made up of the 2
  elements sodium and chlorine
• Like salt, compounds usually look different
  from the elements in them
                Mixtures
• Who enjoys eating pizza and pop for lunch?
• If so, then you enjoy 2 foods that are
  classified as mixtures
• A mixture, such as pizza or pop, is a
  material made up of two or more
  substances that can be easily separated by
  physical means.
        Mixtures
• Heterogeneous Mixtures:
• Unlike compounds, mixtures aren’t always
  made of the same proportions of the
  substances that make them up.
• Remember that pizza? The chef doesn’t
  measure out precisely how much of each
  topping is sprinkled on. Plus, you can easily
  see most of the toppings on the pizza
• A mixture in which different materials can be
  distinguished easily is called a
  heterogeneous mixture
• Other examples: granite, dry soups, concrete
                  Mixtures
• Homogeneous Mixtures:
• Remember that pop? It’s an example of a
  homogeneous mixture
• A homogeneous mixture contains 2 or more
  substances blended evenly throughout
• These mixtures are also known as solutions
• Solutions remain constantly and uniformly mixed
• Other example: Vinegar
             Mixtures


• What kind of mixture is a solution??
Element, Compound, Mixture
                 Colloids
• A colloid is a type of mixture that never
  settles
• Its particles are larger than those in
  solutions but not heavy enough to settle
• Examples: Milk, paint, fog
                    Colloids
• Detecting Colloids:
• To tell for certain if a liquid is a colloid, pass a
  beam of light through it
• A light beam is invisible as it passes through a
  solution, but can be seen when passing through
  a colloid
• This occurs because the particles in a colloid are
  large enough to scatter light
• The scattering of light by colloidal particles is
  called the Tyndall effect
• Can you think of any other colloids?
               Website
• http://www.brainpop.com/science/matter/c
  ompoundsmixtures/index.weml
Properties of Matter


       Section 2
      p. 526-533
          Physical properties
• Physical properties are observations that you
  make without changing the identity of the
  substances that make up the material
• For instance, you can stretch a rubber band or
  bend a piece of wire
• The ability to stretch or bend are physical
  properties
• Some other physical properties are color, shape,
  size, melting point, and boiling point
     Physical Properties

• Appearance:
• How would you describe a tennis ball?
  (shape, color, state of matter)
• How would you describe a soft drink?
  (color, state of matter, taste)
• You could also measure its volume and
  temperature—these are all physical
  properties
             Physical Properties
• Behavior:
• Some physical properties
  describe the behavior of a
  substance
• For instance, objects containing
  iron (I.e. safety pins) are
  attracted by a magnet
• Remember that soft drink? If you
  were to knock it over, it would
  spread onto the table and floor—
  the ability to flow is a physical
  property of liquids
 Physical Properties
    to Separate

• Have you ever licked the icing from the middle of
  a sandwich cookie?
• If so, then you’re using physical properties to
  identify the icing and separate it from the rest of
  the cookie
• You can use other physical properties to
  separate such as using a sifter to separate
  poppy seeds from sunflower seeds
• Or sand from iron fillings by using a magnet
          Physical Change
• If you break a piece of gum, you change
  some of its physical properties—shape
  and size
• However, you haven’t changed the identity
  of the materials that make up the gum
• Each piece still tastes and chews the
  same
          Physical Change
• A physical change is any change in size,
  shape, or state of matter
• These changes might involve energy
  changes, but the kind of substance—the
  identity of the element or compound—
  does not change!
         Physical Change


So, does a change in state mean that a new
           substance has formed?
  Physical Change to Separate
• I some parts of the world, water is very
  scarce, many such areas lie near the sea
• They obtain their drinking water by using
  the physical property of boiling point to
  separate the the salt from the water
• This process is called distillation
• In distillation, you use an apparatus to
  vaporize and condense liquid, leaving the
  solid material behind
        Chemical Properties
• Have you ever seen the warning labels on
  paint thinners and lighter fluids that read
  ―FLAMMABLE‖
• Flammability is a chemical property
• Burning produces new substances during
  a chemical change

								
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