Chemical Changes

Stella L. Harvey               Horace Mann School
                               8050 S. Chappel Street
                               Chicago IL 60617
                               (312) 535-6640        

Objectives:

The second grade students will investigate some chemical changes and reactions 
and should be able to identify at least four characteristics that indicate a 
chemical change.  These investigations will be conducted through experiments.

Materials Needed:

- glasses - one for each student
- orange juice - half gallon 
- water
- baking soda
- candle
- paper
- vinegar
- hot plate
- bread - white
- spoons (plastic)
- knives (plastic)
- eggs (2 uncooked)
- cucumber 
- pickles - 1 large jar
- sugar
- milk - half gallon  
- ziploc bags
- paper towel
- baby food jars- 4
- tablespoons - 4
 
Strategies:

Activity 1:

1.  Display various items and talk about different physical and chemical 
    changes.
2.  Discuss the definitions of physical and chemical changes.
3.  Students will observe the differences between a piece of toast and a plain 
    slice of bread.  Students will remove these items from the ziploc bag at 
    their group station.  Scrape the brown material from the bread.  Ask if they 
    can make the brown material white again?  Try and see if it can be done.  
    Since you can't do this, it's a chemical change. 

Activity 2:

1.  Let the children observe the burning of a candle.  A physical change is 
    represented by the melt down of the wax candle into liquid wax.  (Caution 
    the observers to be careful.)  Some of the liquid wax changes to a gas which 
    burns.  This burning of the wick and gaseous wax is an example of a chemical    
    change.    

Activity 3:

1.  Let the children observe a raw egg.  Stirring the egg is a physical change. 
    In a small pan cook the second egg.  Talk about what kind of change took 
    place. (chemical) 
         
2.  Give each group a few slices of fresh cucumber.  Let them observe the whole 
    cucumber first.  Students will also observe pickle slices and whole pickles.  
    Talk about the differences between the cucumber and pickle slices.  Why do 
    they look different?  Children may respond by answering that a chemical and 
    physical change occurred.  Children should be able to note a change in 
    color, taste, and texture. 
     
Activity 4:
 
1.  Let the children observe a sheet of paper.  Teacher burns part of the paper. 
    Discuss fire, smoke, odor, and colors.  What happened to the paper?  Why?  
    The paper has undergone a chemical change.  The original substance has 
    changed to something else and can't be returned back to the original 
    substance. 

2.  Demonstrate making orange soda.  Fill a glass, one  half full of water, and 
    the other half full of orange juice.  Add a half teaspoon of baking soda and 
    a half teaspoon of sugar.  Work in groups to make your orange soda.  What 
    happened?  What did you notice?  This is a chemical change.  The bubbles are 
    carbon dioxide which was caused by a chemical reaction. 

Activity 5:

1.   To demonstrate separating milk into its solid and liquid parts, let the  
     children or group leader fill the baby food jar with fresh milk.  Students 
     will add 2 tablespoons of vinegar and stir.  Allow the jar to sit for two 
     to three minutes.  The milk separated into two parts; a white solid and a 
     clear liquid.  Why?  Milk is a mixture of liquids and very tiny particles 
     that are spread throughout the liquid.  Vinegar causes the small 
     undissolved particles to clump together, forming a solid called curd.  The 
     liquid portion is referred to as whey. 
                
Performance Assessment:

    The learner will demonstrate his/her understanding of a chemical change by 
    selecting at least two of the experiments to draw, color, and write three or 
    more sentences that explains their observations. 

    The learner may also complete a data chart. 

References:

   Kitchen Chemistry, Carson-Dellosa Publisher
   Simple Chemistry Experiments with Everyday Materials, Loeschnig,
     Louis V., Sterling Publishing Co., Inc.