Physical And Chemical Changes

Carolus Love                   Hoyne School
                               8905 S. Crandon
                               Chicago Il 60617
                               (312) 535-6425
Objectives:

  Grade 2
   1. The students will identify some physical changes of matter.
   2. The students will identify some chemical changes of matter.
   3. The students will distinguish between physical and chemical changes.
   4. The students will classify changes as physical or chemical. 

Materials Needed:
                     
   skim milk                  liquid detergent       microwave
   vinegar                    hot plate              salt
   baking soda                white bread            straws
   toaster                    toast                  sauce pan 
   molded ice                 water                  cookie cutters
   bundt pan                  pyrex bowls            pictures
   plastic cups/tops          whipping cream         Duncan Hines Cupcake Mix 
   2-glass bowls              orange juice           letters
   aluminum foil              poster boards          tape
   glue                       markers                measuring spoons 
   strainers                  large spoons           flour

Strategy:

Introduction
   
   Discuss the meaning of the word change.  Give examples.  You were in first
   grade last year and now you are in second grade.  Turn the television to 
   another channel when you want to see a different program.  Elicit other
   examples of what change means to them.

   Activities

   1. Show the students a ball of play dough.  Ask who can tell me what this is.
      Allow students to take turns manipulating the play dough into various 
      shapes by using cookie cutters.  Ask the following questions:  Did it 
      change into a new substance?  Is it still play dough?  This is called a 
      physical change. 

   2. Demonstrate the proper way to make a bubble.  Pour bubble solution into
      foil pan.  Place the straw in the pan and blow into the straw.  The team
      who blows the biggest bubble within 30 seconds is the winner.  Is it
      still a soap solution?  Therefore, this is a physical change.

   3. Observe ice change from a solid to a liquid and then to a gas (steam).   
      Put a piece of ice into a pot and set it on the hot plate until it 
      melts, then set a piece of aluminum foil over the pot.  Students will 
      explain what they observed and draw pictures to illustrate how the ice
      changed.  Although the ice changed from one phase to another, it is still
      water and can return back to the solid state again.

   4. Demonstrate how butter is made.  Empty a 1/2 pint of whipping cream into
      a plastic container and take turns shaking it.  Observe how it looks, 
      sounds and feels.  Pour off the milk and put a pinch of salt in it.
      If I melt the butter and pour it back into the liquid and stir it, can we 
      get the whipping cream back?  Their response should be yes.  This is 
      another physical change.  You can sample  the butter on crackers or bread.

Strategy:
  
   Define chemical change as when matter is changed into something new or a 
   different substance.                                                       
     
   Activities   

   1. Demonstrate the procedure for making glue.  Put a pint of skim milk and 
      six tablespoons of vinegar into a glass sauce pan and heat slowly, 
      stirring continually.  When the milk forms small curds, remove it from the 
      heat.  Pour off the liquid.  Dry the curds.  Then add 1/4 cup of water and 
      a level tablespoon of baking soda and stir.  What did you notice? They 
      should have noticed some bubbles.  Is it still milk?  Is it still baking 
      soda?  Is it still vinegar?  Is it still water?  Since we do not have the 
      same materials we began with, this is called a chemical change. 
       
   2. Students will observe the difference between a piece of toast and a plain 
      slice of bread.  If you scrape the brown material from the bread can you 
      make the brown material white again?  Try  and see if it can be done.  
      Since we can not do this, it is a chemical change. 
     
   3. Demonstrate making orange soda.  Fill a glass 1/2 full of water and the 
      other half with orange juice.  Add 1/2 teaspoon of baking soda and 1/2 
      teaspoon of sugar.  Work in groups to make your soda.  Ask the same type 
      of questions with each substance as in previous experiments.  This is a  
      chemical change.  The bubbles formed carbon dioxide which was caused by a 
      chemical reaction.  

   4. Teacher and assistant will help students in preparing cupcakes.  Examine 
      the cupcake mix before and after it was cooked.  How did it look?  Did it 
      change?  The baking powder is what caused the cupcakes to rise.  Is it 
      still flour?  Is is still baking powder?  Is it still water?  Their 
      response should be no.  Therefore, this is a chemical change because we 
      have a new substance formed. 

Performance Assessment:
   1. Given pictures of various physical and chemical changes, students will put 
      them under the correct heading on the chart. 
   2. The students will demonstrate their understanding of changes by explaining 
      the difference between physical and chemical change. 

References:
Vancleave, Janice Pratt.  Chemistry For Every Kid. John Wiley and Sons, Inc.
     New York:  1988.

Walpole, Brenda.  Science Experiments to Amuse and Amaze Your Friends.  Random 
     House, New York:  1988.