The Chemistry of Water

Virginia Harris                DuSable High School
7031 S. Bennett Avenue         4934 S. Wabash Ave.
Chicago, Illinois 60649        Chicago, Illinois 60615
312-493-7869                   312-536-8600

Objective:
   
  Grade level: Ninth

1. To discuss the phenomenological properties of water.
2. Discuss and demonstrate solubility of liquids.
3. Students will define and give examples of expansion.
4. Demonstrate surface tension individually and as a group.
5. Students will make a water molecule combining the class molecules together 
   forming water.    

Materials needed:

   (For each student.)
Activity 1 

  One large beaker, black pepper, one small needle, water, and a dish washing 
  detergent. 

Activity 2

  One large styrofoam ball, two small styrofoam balls, two toothpicks. 
  
Strategy:
       
    Review properties of water showing the natural existence of water in three 
    states.  Discuss and demonstrate the solubility of water using sand, sugar, 
    oil, vinegar and salad dressing.  The students will readily recognize that 
    all substances do not dissolve in water and that there are other liquids 
    that are good solvents. 
    
    Students will observe a can of coke that has been left in the freezer over- 
    night.  What happened?  Why?  Car radiators sometimes freeze in winter. Why? 
    
    In Activity 1, students will fill a large plastic container with water. 
    Sprinkle the surface of the water slightly with black pepper.  Discuss 
    observations.  Drop a dish washing detergent in the center of the dish. 
    Observe what happens.  Class will discuss observations. 
    
    Place some water in a large plastic cup.  The water can be at any level in 
    the cup.  Let the water stand for two or three minutes.  Place a small 
    needle on the surface of the water.  Observe what happens?  Why? Place a 
    small needle on the surface of the water using forceps.  Discuss    
    observations.  Was it easier to place the needle on the surface of the water 
    with your fingers or with the forceps?  Class will discuss their 
    observations and give reasons as to what they think happened. 

    
    In Activity 2, students will construct a water molecule showing how the 
    hydrogen atoms are bonded to the oxygen atom using toothpicks.  The class 
    will bond their molecule with another molecule (in a straight chain) to show 
    how water is formed.  The water molecule looks very much like a Mickey Mouse 
    hat.  It has a covalent bonding and is polar because of the 105 degree angle 
    between the hydrogen atoms. 
     
  Conclusion:                                                             
                                                                                
    The natural existence of water in three different forms is indeed a 
    phenomenon.  Plants and animals cannot survive without it.  We use it in 
    every aspect of our daily lives.  Solubility, expansion and surface tension 
    are some of the properties that makes water unique. 

    We should not waste or pollute water because there are some countries who do 
    not have any water.  We should always remember those without and create ways 
    to help.