Physical And Chemical Changes

Ann Sims                       Dyett Middle School
                               555 East 51st Street
                               Chicago, IL 60615
                               312-535-1825

Objectives:

The student will
    1.  define the terms; physical change and chemical change.
    2.  identify the different changes as they relate to matter.

Materials:
    
    For each group of three students:

    1.  candle, matches, modeling clay
    2.  3 sheets of paper, watch glass
    3.  hot plate, apron, table salt
    4.  2-test tubes, dropper bottle of 0.1M silver nitrate
    5.  magnesium ribbon (1 cm long), 1M hydrochloric acid
    6.  construction paper, household bleach

Suggested Strategy:
   
    1.  Make pictures using bleach on construction paper as a P/A.
    2.  Place a candle on a small piece of modeling clay, so that it is well 
supported.  Light the candle and allow it to burn while you continue with the 
rest of the investigations.  Record your observations. 
    3.  Tear one sheet of paper into strips.  Wet another sheet of paper.  Tear 
the third sheet into small pieces and place them on the watch glass.  Light the 
pieces on the watch glass with a match.  Let them burn completely.  Record your 
observations of the three sheets of paper. 
    4.  Add a small scoop of table salt to a test tube that has been half-filled 
with tap water.  Place your thumb over the top of the test-tube and shake to 
dissolve the salt.  Record your observations.  Using the dropper, add five (5) 
drops of silver nitrate to the salt water solution.  Record your observations.  
Add a scoop of salt to a half filled test-tube of tap water, heat over the hot 
plate for twenty minutes.  Record your observations.
    5.  Place a small piece of magnesium ribbon in a test-tube.  Add five (5) 
drops of hydrochloric acid to the test-tube.  Touch the bottom of the test-tube 
with your fingertips.  Record your observations.

Conclusions:

    The two kinds of changes that occur in matter are physical and chemical.  In 
a physical change, no new substance is formed.  However, physical properties 
such as size, shape, color or phase may change.  In a chemical change, one or 
more new substances with new and different properties are formed.  Burning and 
rusting of iron are examples of chemical changes.