JetStream - An Online Weather School Learning Lesson: Heavy Air

The Atmosphere Learning Lessons

1.	AM in the PM
2.	Heavy Air
3.	A Pressing Engagement
4.	Going with the Flow
5.	Crunch Time
6.	The "Wet" Barometer
7.	The "Dry" Barometer
8.	Melts in your Bag, not in your Hand
9.	Canned Heat
10.	It's a Gas, Man
11.	Sweatin' to the Coldies
12.	The Rain Man
13.	Water, Water Everywhere

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Learning Lesson: Heavy Air

OBJECTIVE	Show that air has weight.
OVERVIEW	After balancing two inflated balloons, the air is removed from one balloon throwing the balance off.
TOTAL TIME	5 minutes.
SUPPLIES	Yard/meter stick Two large balloons String Scotch tape
PRINTED/AV MATERIAL	None
TEACHER PREPARATION	You can have someone hold the string or you may want to have a piece of string hanging from the ceiling before class.
SAFETY FOCUS	Severe thunderstorm safety rules

Background

Air is all around us. This air is composed of atoms and molecules. Despite their small size, the quantity of atoms and molecules exert weight on us known as pressure. Since our bodies are designed to live in this environment, we do not notice the pressure.
Procedure

Blow up both balloons so they are the same size. Tape one balloon to each end of the yard/meter stick. Tie a string to the center of the stick and adjust it so the stick balances when held by the string. Tape the sting in place to prevent it from slipping. Ask the students, "If one end were heavier, would the heavier end move up or down?". Supporting one balloon, have someone carefully deflate the other balloon. Try poking the balloon with a pin in its neck to prevent the balloon from tearing apart as it pops. Release the remaining balloon and ask the students to explain what happens.
Discussion

Since the inflated balloon weighs more than the deflated one, the side of the inflated balloon will drop. Imagine the weight of air if that balloon were now 15 miles (24 km) tall. That is actually what is occurring at this moment in your classroom. When we measure air pressure, we are measuring the weight of a column of air 15 miles (24 km) high directly over us.
Live Weatherwise

Severe Thunderstorm Safety The weight of molecules also affects the weather. One measure of the severity of a thunderstorm is the wind speed. In addition to the size of hail, the National Weather Service defines a severe thunderstorm as one containing wind speed of 58 mph (50 kts) or greater. The weight of all of the molecules in wind of 58 mph (50 kts) can create hazardous weather conditions such a blowing down phone and power lines, trees, and make driving hazardous. When the National Weather Service issues a Severe Thunderstorm Warning it means a thunderstorms with wind gusts to 58 mph (50 kts) or greater and/or hail size of 3/4" or greater is occur or about to occur near you. Discuss severe thunderstorms with your family. Everyone should know what to do in case all family members are not together. Discussing disaster ahead of time helps reduce fear and lets everyone know how to respond during a severe thunderstorm. Take an American Red Cross first aid and CPR course to learn how to treat burns and how to give rescue breathing and administer CPR. Everyone should know how to respond, because severe thunderstorms can strike almost anywhere at anytime. Postpone outdoor activities if thunderstorms are likely. Many people take shelter from the rain, but most people struck by lightning are not in the rain! Postponing activities is your best way to avoid being caught in a dangerous situation.

Fast Facts

Baseballs travel farther in moist air than in dry air. Water molecules consists of two hydrogen atoms and one oxygen atom. Hydrogen atoms are the lightest elements in existance. Oxygen atoms are eight times heavier.

The combination of two hydrogen atoms and one oxygen atom takes up more space as compared to lone oxygen atoms. Therefore, moist air in any give space, means less stand-alone oxygen atoms which means less weight.

Since there are less molecules and atoms in the same space there is less resistance for objects that travel through the air. With less air resistance, the farther objects can fly, such as baseballs.

Back: Air Pressure

National Weather Service Southern Region Headquarters 819 Taylor Street Fort Worth, Texas 76102	www.srh.weather.gov Updated: January 6, 2005

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