2003 Virginia SOLs
While we need air in order to breathe, many students do not realize that air is a form of matter. Because we live our entire lives in an environment in which we are always surrounded by air, we often forget that air is actually matter, and has a measurable mass. The mass/matter quality of air is what causes air pressure; this affects many things ranging from weather patterns to the inflation of sports balls, such as the soccer ball that will be used in this activity.
It is important to know that air pressure can be measured in several units. Among these are pounds per square inch, millimeters of mercury, and atmospheres. In this lab, we will use atmospheres. For convenience, scientists have set 1 atm = to standard air pressure.
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To print out a copy of the Data Sheet only, click here.
Mass of jar lid: ______________ g
Mass of inflated ball and lid: ____________ g
Radius of the ball: _____________ g
Mass of partially deflated ball and lid: ___________ g
Mass of the escaped air:
(Mass of inflated ball - Mass of partially deflated ball)
Volume of air inside the ball:
(V = (4/3)pi*R3)
Density of the air at normal pressure:
( Density = Mass of air/ Volume of air)
* You can find the density of air at normal pressure because a ball inflated to regular game pressure is at about twice the pressure of regular outside air (measured as one atmosphere). Thus, when you let out the "extra" air in letting the ball deflate to standard room air pressure, you are letting out about half of the air, or one atmosphere's worth.
Answer the following questions on a separate sheet of paper:
What is inside the ball? What does the mass measurement include?
Does the soccer ball maintain a constant volume as air is added to it?
As the ball was being inflated, what was "pushing" on the sides of the ball?
Did the mass of the ball change as it was inflated? What do you think caused the change in mass?
The accepted value for the density of air is about 1.3 g/L, or .0013 g/cm3. How close was your measurement of the density? What may have caused the difference between your answer and the accepted value?
Students with Special Needs
All students should be able to participate in this activity.
Click here for further information on laboratories with students with special needs.