Matter – Physical and Chemical Properties

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					               Physical and Chemical Properties and Changes


A. Physical Property – any characteristic of matter that can be observed with the
   senses without changing the identity of the material.
      1. Physical properties include color, shape, smell/odor, taste, mass, volume,
          and density.
      2. Density – the amount of mass in a given volume;
          a. A golf ball would have greater density than a table tennis ball.
          b. The formula for density is D=M/V.
      3. Density can be used to identify unknown substances; a person could
          determine the composition of a piece of jewelry by comparing its density
          with the density of a known substance such as silver or gold.
      4. State of Matter – whether a substance is a solid, liquid, or a gas at a
          particular temperature and pressure
      5. Some physical properties are extensive or size-dependent (length, width,
          height, volume, and mass) while others are intensive or size-independent
          (density, color, state).
      6. Other examples of physical properties are: solubility in water (the ability
          of substance to dissolve in water), melting point, boiling point, freezing
          point, hardness, ductility, malleability, and conductivity.


B. Chemical property – characteristic of something that allows it to change to
   something new.
      1. Chemical properties include flammability, toxicity, and reactivity with
         oxygen; when a half eaten apple turns brown in the air, a chemical
         reaction with oxygen has occurred.
      2. Silver and gold have lower reactivity than many other metals, which helps
         make them good choices for jewelry.
      3. Chlorine compounds change the chemical properties of pool water,
         making it more acidic in order to eliminate algae, bacteria, and insects.
         a. Standing water, without added chlorine, can become a breeding
             ground for insects, such as mosquitoes.
         b. Plants, algae, and bacteria can make a pool unfit for swimming.
         c. The more acidic chlorinated pool water can also irritate the skin and
             eyes of swimmers.
      4. Also, the ability or inability of a substance to combine with another
         substance is a chemical property.
         a. The ability of iron to form rust when combined with air is a chemical
             property to iron.
         b. The inability to of neon to combine with most other substances is a
             chemical property of neon.
   Practice problems – Identify each of the following as an example of a physical
   property or a chemical property.

   1.  Silver tarnishes when it comes in contact with hydrogen sulfide in the air.
   2.  A banana is yellow.
   3.  A sheet of copper can be pounded into a bowl.
   4.  Barium melts at 725 C.
   5.  Gasoline is flammable.
   6.  A diamond is the hardest natural substance.
   7.  Helium does not react with any other element.
   8.  A bar of lead is more easily bent than is a bar of aluminum of the same size.
   9.  Potassium metal is kept submerged in oil to prevent contact with oxygen or
       water.
   10. An apple will turn brown is left in oxygen.
   11. Diamond dust can be used to cut or grind most other materials.
   12. Acid in tomato sauce can corrode aluminum foil.
   13. Rocks containing carbonates can be identified because they fizz when
       hydrochloric acid is applied.
   14. A piece of charcoal, which is mostly the substance carbon, glows red, gives
       off heat, and becomes a gray ash.


                    Matter - Physical and Chemical Changes

A. Matter can be changed two ways: physically or chemically.

B. Physical changes – any change in size, shape, form, density, or state where the
   identity of the matter stays the same
   1. Does not change the type of matter; nothing new is formed
   2. Cutting a watermelon into slices is an example of a physical change.
   3. Change of state is a common physical change.
           a. solid to liquid (ice melting)
           b. liquid to solid (water freezing)
           c. liquid to gas (water boiling and creating steam)
           d. gas to liquid (water vapor condensing into water such as when dew
               forms)
           e. solid to gas (dry ice, solid air fresheners, solid iodine)
   4. Weathering of Earth’s surface is a physical change in nature.
   5. Making a mixture (two or more types of matter combined)
          a. not in specific amounts
          b. can be separated physically

C. Chemical changes – one material changes into a different material with different
   properties or characteristics
   1. In a chemical changes, new materials are formed that are different from
      the starting or original materials.
2. Examples of chemical changes include digestion, photosynthesis, paint
   drying, the formation of rust, and oil burning.
3. A chemical change cannot easily be reversed.
4. Signs of chemical changes include the release or absorption of energy in
    the form of light, heat, or sound; formation of a gas or solid, not from a
    changes in state, can indicate a chemical change.
5. Leaves changing color indicates a chemical change in nature.
6. Acid rain is a form of unnatural chemical change.
7. Terms such as decompose, explode, rust, oxide, corrode, tarnish, ferment,
   burn, or rot generally refer to chemical changes.