Change Of State

Bernard Hudson                 Morton Career Academy
                               431 N. Troy Street  
                               Chicago, Il. 60612    
                               (312) 534-6791

Objective:
      
      The students will
        1.  Note the change of state of Butyl Stearate (BS).
        2.  List the characteristics of BS in solid and in liquid forms.
        3.  Note the temperature at which liquid goes to solid.
        4.  Note the temperature at which solid goes to liquid.
        5.  Chart the temperature vs. time change solid to liquid.
        6.  Chart the temperature vs. time change liquid to solid.

Materials  needed: 
    
    For a class of 15:
         1.  15 Test Tubes
         2.  30 Beakers
         3.  15 Thermometers
         4.  15 Hot Plates
         5.  500 mL Butyl Sterate
         6.  Ice/Water 
         7.  15 pr. Goggles   
         8.  15 Aprons 
         9.  Paper Towels 
        10.  Clock/Watch
        11.  1 each, package gelatin ('Jello' brand or equivallent) & 1 prepared 
              model
        12.  1 each, package 'Kool-Aid' brand drink mix & 1 popsicle         
        13.  1 each, pitcher, mixing bowl, spoon

Strategy:

         1.  Discuss how mother makes 'Jello'.
         2.  Ask students to help make 'Jello'.
         3.  Display solidified 'Jello', note if it is wet or dry.
         4.  Introduce the terms solid and liquid. 
         5.  Discuss how 'Jello' changes from liquid to solid.
         6.  Ask students to predict what may happen if we heated solid 'Jello'. 
         7.  Demonstrate how solid 'Jello' returns to liquid with heat.
         8.  Do the same procedure with 'Kool-Aid' and a popsicle.
         9.  Have children list physical properties of both substances and note 
             on their worksheets which properties change with the changing 
             states and which properties remain the same.
        10.  Have students read aloud laboratory directions and tell what they 
             are to do when they move to the laboratory.   
        11.  Have students describe butyl stearate as a liquid and experiment 
             with placing a test tube of this liquid in boiling water and in ice 
             water.
        12.  Have students repeat changing states several times.
        13.  Ask what is required to change the state.  (Heat must be added or 
             removed).
        14.  After students have made the connection between temperature and 
             state, ask them if they think they could find the temperature at 
             which a change of state takes place.
        15.  Supply a thermometer and let students find the temperature of the 
             two water baths.
        16.  Ask students to place their thermometer in liquid Butyl Stearate 
             and place the test tube in the ice water bath.  They must chart the 
             temperature drop until all the liquid solidifies. 
        17.  Repeat going from solid back to liquid.
        18.  Teacher will graph one or more of these charts on the front board 
             and discuss the meaning of the results.