Water Cycle - Atmosphere (4)
Pre Lab 

   
OBJECTIVES:
  • Exploring how the atmosphere and hydrosphere interact.
  • Discovering the effect of air pressure.  
VOCABULARY:
  • aerodynamic
  • atmosphere
  • hydrosphere
  • weather
MATERIALS:

Students demonstrate that air is strong.

BACKGROUND:

The atmosphere is almost invisible to the majority of people.  Most young children do not even realize that air is a “thing.”  The atmosphere is very powerful especially if you consider that weather is caused by the many interactions of temperature, moisture, pressure, and wind.  Ancient people had a difficult time trying to figure out exactly what was in the atmosphere.  In the fourth grade, emphasis is on how the elements of temperature, pressure, and wind interact.   

When we discuss air pressure,  we don't usually realize that air presses on every side of an object.  Air exerts its force in all directions equally.  Only in a vacuum, where there is no air, is an object free from pressure.

Air pressure is real.  In our atmosphere air moves in part because of unequal heating of land and water that creates air currents.  The rotating Earth also causes movement.  The important concept to emphasize is that air is a real substance, that interacts with the hydrosphere and land (lithosphere) to create different weather patterns. 

PROCEDURE:

Review with students that air is a substance that has properties. Either do the demonstrations suggested below or have the students perform them.  The activities emphasize that air pressure is all around us and we can use its “magic” if we understand it.

  1. Blow up a balloon and ask students how to make the balloon fly.  Hopefully the students will realize that just releasing the unknotted tip will let the balloon propel backwards.  Why?  The air is released and the force of the air propels the balloon forward.  [For every action, there is a reaction.]
      
  2. A simple experiment to illustrate  that air exerts a pressure is to place a balloon in an empty jar.  Blow into the balloon and inflate it in the jar.  Notice that the balloon will swell out until it touches the glass sides.  A few more puffs, and it becomes an easy matter to lift the jar with the air of the balloon.
     The air pressure inside the balloon exerts its force in all directions, pressing the walls of the balloon so tightly against the glass jar that it cannot easily be pulled free unless some air is released from the balloon.
      
  3. How can you make the little ball in the Bernoulli pipe stay afloat?  Blow into the pipe.  Just a stream of air increases the pressure below and makes the ball look like it is floating.  You have increased the air pressure below the ball, which keeps the ball afloat. 
      
  4. Can air be captured to help machines fly?  Yes, take for instance the puddle jumper.  If you curl the base away from your body and release it, notice that the puddle jumper acts like a helicopter for a while.  The design of the toy’s wings helps to direct the air under the wood to help keep it afloat.

[Dictionary]  
  [Back to Water Cycle Grid]  [Back to Atmosphere (4)]