Chemistry Is A Gas

Blake, Thelma B.                      Louis Worth Experimental School
                                      536-8910
                          

Objectives:

The student will be able to apply the conventional gas laws in the 
determination of volume changes resulting from changes in temperature, 
pressures, or number of moles of the gas. 

Apparatus Needed:
 
Hypodermic Spring Scale, weights or books, hot plates, gas can, glass 
tubing, rubber stopper, 500 ml beakers, 125 ml flasks, tongs, clamps, 
gloves, and balloons. 
    
Recommended Strategy:

The following strategies demonstrate the use of Boyle's Law  which is 
                               P1V1=P2V2.

1. Hypodermic Syringe Scale (Elasticity of a Gas Apparatus):  Use 
   weights or books on top of the syringe scale to measure pressure 
   with this additional weight. 
2. Can Carbonated Water:  You've seen Boyle's Law in action when you've 
   shaken a can of pop.  As you open it the liquid ends on you and your 
   surroundings. 
3. Atmospheric Pressure:  Use a gas can and boil a few ounces of water 
   in it, remove from heat and close the can.  Let the can cool.  The 
   steam in can cools, condenses, reducing the vapor pressure inside 
   the can; the normal external atmospheric pressure is greater than 
   the internal pressure and the can collapses.  Air pressure is a force 
   that acts on the outside surface.

The following strategies demonstrate the use of Charles' Law 
                               V1T2=V2T1.

1. Temperature-Volume Demonstration:  The temperature-volume 
   relationship of a gas can be seen by inverting a round-bottom thick 
   wall flask having a piece of glass tubing inserted in a rubber 
   stopper in its neck into a beaker of cold water.  First boil a small 
   amount of water in the flask and immerse the flask into the beaker 
   of cold water.  The water level in the flask increases.  When an 
   additional amount of hot water is poured over the flask, it will 
   cause the water level inside to decrease. 
2. Demonstrations with Balloon:  Cover the mouth of a small flask with 
   a rubber balloon and gently heat the flask.  The balloon will 
   inflate.  Use another small flask and let a small amount of water 
   boil in it.  Remove from heat and place a balloon over the mouth of 
   the flask.  The balloon is drawn into the flask.