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					Notes for Chapter 2: Classification of Matter

Atoms – smallest unit of an element that has the properties of that
element
Element – a substance that cannot be separated or broken down into
simpler substances by chemical means
Compound – as substance made of atoms of two or more different
elements that are chemically combined
Molecule – the smallest unit of a substance that keeps all of the physical
and chemical properties of that substance
Mixture – a combination of two or more substances that are not
chemically combined




  1. _____________________ has mass and occupies space.
  2. Elements (can or cannot) be broken down into simpler substances.
  3. Pure substances include ___________________ and
     ____________________but not __________________________.
  4. Two atoms of hydrogen chemically combined with one atom of
     oxygen form one _____________________ of water.
  5. ________________ are formed from pure substances that are not
     chemically combined.
                    Physical Properties

                       - Often easy to see
                 - Can often use your senses
                              Shape
                              Color
                               Odor
                          Lack of color
                              Mass
                             Volume
                             Density
                   - Have to measure others
                          Melting point
                           Boiling point
                             Strength
                            Hardness
                Ability to conduct elec. or heat

- Tend to be consistent for pure substances, so can be used to
                             identify

                  - State (solid, liquid, gas)
            -Can be used to help determine uses!

                    Chemical Properties

       - Not as easy to observe as physical properties
 Reactivity (how easily it forms compounds with other atoms)
How does it change into a new substance? (by breaking apart or
                         by combining)
                          Flammability

   - A chemical has these properties even when you can’t see
                              them!
 Key: You can observe physical properties without changing the
  identity of the substance. You can observe chemical properties
 only in situations in which the identity of the substance changes.

Characteristic properties – most useful in identifying a substance.
            Same whether the sample is big or small.



Physical changes – affect one or more physical properties without
changing its identity.

Example: breaking a stick. Sanding a piece of wood.

                        Physical Changes




Chemical changes – occurs when one or more substances are
changed into entirely new substances that have different
properties.

 Clues – change in odor, color, fizzing or foaming, smoke, sound,
heat, light or odor.
Undone not by physical means, but by chemical means.
Change of state (liquid, solid, gas)
Are changes of state physical or chemical changes? Why?




                              Alloys
Mixtures made by melting together a metal with one or more other
substances.

Examples
Gold & nickel
Aluminum and magnesium
Iron and carbon (steel)

Why?
Strength/mass/more powerful magnetic

Need drives technology!!

First – meteorites? (iron and nickel)
Bronze – copper and arsenic
Tin & copper – better weapons

Bronze is harder when cool, but easier to melt and work with when
molten

				
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