Chemical Change and Physical Change

Vince Davis Sr.                William Penn School
                               1604 S. Avers
                               Chicago IL 60640
                               (312) 534-1665

Objectives:  

Grade 6
                                                                    
1. To investigate some characteristic of chemical change.
2. To learn that a chemical reaction occurs when two reactants combine
   to form a new product. 
3. To learn that color change is an indicator of chemical change.

Materials:

Activity 1.  vinegar, steelwool, household ammonia, tablespoon, two small
  baby food jars.     
Activity 2. hydrogen peroxide, raw potato, 5-oz.paper.    
Activity 3. iron powder, sulfur powder, one magnet, glass plate.

Strategies:
                          
Activity 1.
1. Fill one-half of one jar with steel wool.
2. Add enough vinegar to cover the steel wool.
3. Write IRON ACETATE on the side of the glass.
4. Allow the jar to stand undisturbed for five days.
5. Pour one tablespoon of the liquid Iron Acetate into the second jar.
6. Add one tablespoon of household ammonia and stir.
7. A green blob forms indicating a reaction.                                 

Activity 2.
1. Fill paper cup one-half full with hydrogen peroxide.
2. Add a slice of raw potato 
3. Look specifically for bubbles of gas.
                  
Activity 3.
1. Combine a half of a teaspoon of iron filings with a teaspoon of sulfur
   powder on a glass plate.
2. Demonstrate to the students that the magnet can separate the iron filings
   from the sulfur powder.
3. Mix both of the elements together and heat.  (This is not to be done in a
   regular classroom, a strong odor will occur and this must be done outside
   or under a vent.)

Performance Assessment:          
  
You and your best friend will vacation at Illinois Institute of Technology 
summer camp.  As a student of the science camp you will be given the opportunity 
to work at a chemistry laboratory.  You must pass several tests before you are 
allowed to work in the laboratory.  Your challenge is to distinguish between 
physical and chemical change.   Fill a paper cup one-half full with hydrogen 
peroxide and add a slice of raw potato to the cup, look specifically for 
bubbles of gas and explain if there's a physical or chemical reaction.  Take a 
sheet of note book paper and tear it in half, explain if there a physical or 
chemical reaction.                       
                                                                  
Conclusion:                                                                

The rusting of iron, the burning of gasoline, the cooking of sugar are all 
examples of chemical reactions.  When a chemical reaction takes place, there is 
always a change in the properties and in the energy of the substances involved 
in the chemical reaction.  Both the physical and chemical properties   of the 
substance are changed.  The Green Blob results in a dark green, jelly like 
substance forming immediately.  The iron in the steel wool combines with vinegar 
to produce iron acetate.  Household ammonia's chemical name is ammonium 
hydroxide.  A chemical reaction occurs as soon as these two liquids combine.  
The raw potatos contains the enzyme catalase.  Enzymes are chemicals found in 
living cells.  Their purpose is to speed up the breakdown of complex food 
chemicals into smaller, simpler, more usable parts.  Catalase from the potato's 
cell causes the hydrogen peroxide to quickly break apart into water and oxygen 
gas. The combining of iron filings and sulfur powder proved that when both 
element are heated a new property is formed, which indicated that a chemical 
reaction has taken place. 

Reference:

Vancleave, Janice. Chemistry for Every Kid. Publisher John Wiley & Sons, Inc.
605 Third Avenue, New York, N.Y. 10158-0012