Vision Props of Signed Numbers

McMiller, Mable                  South Shore High School
                                 933-8190
                           

Objectives:
1.  By titrating with an acid and an alkaline solution, students  will 
    understand that an acid added to an alkaline can become 
    neutralized and by adding more acid, the alkaline solution can 
    become acid. 
2.  After demonstrating the titration of an acid and an alkaline 
    solution, students will perceive that the pH factor, a measure of 
    acidity, neutrality, or alkalinity  of a liquid or a solid in 
    relation to their own bodies. 
3.  Students will gain an understanding of the titration experiment by 
    using the abstract pH factor color charts and transferring the 
    positions to signed numbers (positive or negative numbers). 
4.  By using the abstract tube for their number lines, students will 
    become aware of the importance of the number line and usage of 
    signed numbers. 

Apparatus Needed:
Two 500 ml beakers
Four 200 ml flasks
Four eyedroppers
1M of NaOH (Sodium Hydroxide)
1M of HCl (Hydrochloric acid)
One bottle of litmus paper (blue)
One bottle of litmus paper (red)
One bottle of antacid
One box of baking soda
One bottle of wide range pH 3.0 to 11.0 of phenolphthalein
Six 17cm x 21cm of acrylic glass, colors--red, orange, yellow,
green, clear, and blue.
One long tube about 270 centimeters long and 6 3/4 inch in diameter
Two red plastic book covers and two blue plastic covers

Recommended Strategy:
Be prepared to encourage students to see how the phenolphthalein has 
the property of turning blue in NaOH (Sodium Hydroxide) and turning 
red in HCl (Hydrocloric acid), and adding HCl drop by drop with 
stirring to the sodium Hydroxide will become colorless.  An alkali 
neutralizes of an acid to water and salt solution. 

1.  Pour 1M of NaOH into a 500 ml beaker, and pour 1M of HCl into a 500
    ml beaker.  Pour from the 500 ml beaker of NaOH into a 200 ml flask 
    about 100 ml, and two or three drops of the phenolphthalein into 
    the 200 ml flask of NaOH. 
2.  Repeat the same for HCl.
3.  Take out a blue litmus paper, drop a little of HCl from the 200 ml 
    flask.  The red color shows that hydrochloric acid is an acid.  
    Take out a red litmus paper. Drop a little of NaOH from the 200 ml 
    flask.  The blue color shows that sodium hydroxide is an alkali. 
4.  Have the students to take a blue litmus paper and a red litmus 
    paper, placed under their tongue.  If the red color shows from the 
    blue litmus paper of a pale pink color, they are somewhat acidity. 
    if the blue color shows from the red litmus paper of a pale blue 
    color, they are somewhat alkali.                            
5.  Add HCl (hydrochloric acid) from the 200 ml flask where the drops 
    of phenolphthalein was added to the solution, drop by drop with 
    stirring to the 200 ml flask of sodium hydroxide where the few 
    drops of phenolphthalein was added to the solution.  When the 
    sodium hydroxide becomes colorless, the reaction has neutralized.  
    When the sodium hydroxide becomes red, the reaction is completed. 
6.  Pour NaOH (sodium hydroxide) from the 500 ml into another flask. 
    Add two or three drops of phenolphthalein.  Add sodium hydroxide 
    from the flask drop by drop with stirring to the hydrochloric 
    solution from the 200 ml flask.  When the hydrochloric acid becomes 
    colorless, the reaction has become neutralized.  When the 
    hydrochloric acid becomes blue, the reaction is completed. 
7.  Pour HCl from the 500 ml beaker into another flask.  Add two or 
    three drops of phenolphthalein.  Add two - four teaspoons of an 
    antacid that have aluminum hydroxide and magnesium hydroxide, both 
    are alkali solutions, to the HCl in the flask.  The hydrochloric 
    acid becomes white, the reaction has become neutralized. 
8.  Pour HCl from the 500 ml beaker into another flask.  Add two or 
    three drops of phenolphthalein.  Add l/2 teaspoon of baking soda 
    (sodium  bicarbonate), a source of alkali, to the HCl in the flask. 
    The hydrochloric acid or HCl becomes a clear lime color. 
9.  Divorce chemistry and explain to students that the concentration of 
    hydrogen ions in a water solution is normally a matter of 
    importance for the hydrogen ion is responsible for all acid 
    properties and that includes us.  The concentration of hydroxide 
    ions will be basic or alkali.  In mathematical form it is pH = log 
    1/(H+) and pOH = log 1/(OH-).  The pH is the logarithm of the 
    reciprocal of the molar concentration of the hydrogen ion and the 
    pOH is the hydroxide ion. 
10. Take the two red plastic book covers and measure the amount needed 
    to put inside the tube (about 6 1/4 inches wide) glue the edges 
    with acrylic glue. 
ll. Take the two blue covers and repeat the above.
12. Cut acrylic glass 17.5 x 21cm of red, orange, yellow, green, clear, 
    and blue for a pH chart. 
13. Demonstrate how to use the mathemathical approach for signed 
    numbers using the tube.  Let red represent positive numbers and 
    blue represent negative numbers. 
l4. Place chart on chalkboard--magnetic strips can be used to hold 
    acrylic chart.  Students can select a color from the pH range to 
    represent the continuum of signed numbers. 

If more information is needed on the use of " Vision Props" of signed
numbers, this author can be reached after 6:00 P.M.