THE PRESSURE'S OFF
Grades 3-6

In this lesson and its extensions the students will have an opportunity to learn about air pressure and how it can be raised and lowered. The lesson contains five activities to be completed. One of the activities is a demonstration for safety reasons, but the other four are hands-on activities. This lesson demonstrates why "science doesn't suck."

Take a Look 2 #21: Take a Look

Students will be able to:

• explain that warm air molecules spread out and cold air molecules get closer together
• measure to the nearest centimeter
• read a thermometer using Celsius
• demonstrate that air pressure can lift a mass if a container is forced full of air
• describe that removing the air from inside a straw allows the air pressure outside the straw to push the drink up the straw

Suck it Up

• 2 straws (still in the paper wrappers with a pin sized hole poked halfway down in one straw, the straw that does not have the hole in it should be marked in some way) per group of 2
• 2 clear cups of water per group

I'm Hot - No I'm Not

• one 2-liter bottle per group of 2
• small balloon per group
• container of hot water
• container of cold water
• string that is 20 cm long
• metric measuring device
• thermometer that measure in Celsius

Suck it In (teacher activity)

• glass Ocean Spray jar
• small balloon filled with water
• piece of paper
• matches
• soda straw
• safety goggles

Wind Bag

• 2 Commercially made windbags
• two tables

Balloon Mobile

• 5 clear plastic cups per group
• 1 large balloon per group
• hot water
• bowl of ice

Do the Suck It Up activity.

Give each group of two students two straws that are still in the paper wrapper. Instruct the students to take the wrapper off of their straws and to "suck" the liquid out of the cups. One of the students will be successful in this and the other student will have great difficulty. Ask if any of the students can explain why only half of the students were successful. Allow for the students to brainstorm. Tell the students that as they view this film they will learn some things about "sucking" liquids through a straw.

The title of this video is Air Pressure. Group 1, I would like for you to be watching to find out what cause cups to stick to a balloon. Group 2, I want you to be watching to explain why we don't "suck" air out of a straw.

BEGIN the video Take a Look 2 #21 after the lady says "when the air pressure is dropping, we could be in for stormy weather" and right before where the boy picks up the juice carton . PAUSE after the lady says "That's air pressure at work." Discuss how the air did work. Do the Wind Bag activity at this point. Spread the two commercially made windbags on one of the tables. Turn the second table upside down and place it on top of the first table. Ask for two windy volunteers, to come to the front of the room and lift the table on top without using anything but their mouths. If the students say it can't be done, do some brainstorming with the students on way to accomplish this feat. When they arrive at a plan, ask the two volunteers to implement the plan. Ask the remaining students to predict if they will be successful. (The two volunteers will blow into the windbags and will lift the table.) Ask the students if they think the windbags can lift the table if a student is sitting on top of it. Make some predictions and try the student on top of the table. They will be successful in accomplishing this feat. Talk about other places an object like a windbag could be useful. RESUME the video and PAUSE after the lady says "When you take air from inside of the straw the air pressure on the outside of the straw pushes the drink up the straw. Ask a student to explain in his/her own words what just happened in the video. If some need to view that segment again, you will want to rewind at this point. FAST FORWARD to the question mark (?) and pause after "Do you remember how a straw works?" Allow students to answer the question. RESUME play and PAUSE after the explanation. FAST FORWARD to the children pumping up the balloon. RESUME the video and STOP after the question "How long do you think the cups will stick?" Ask the students to make some predictions as to how long they think the cups will stick to the balloon. Ask for an explanation of why the cups stick to the balloon. (The cups were heated by the hot water therefore the air inside the cup is warm and the molecules are farther apart. The cup is cooled very quickly and then placed against the balloon. The air then becomes cool and the air molecules are closer together allowing room for more air molecules, but the balloons seals the cup leaving the pressure inside the cup lower than the pressure on the outside of the cup.) Allow the students to do the activity Balloon Mobile. Fill the cups with hot water. One by one, pick up the cups, throw the water into a sink or bowl, and place the cup in the ice. Immediately place the lip of the cup against the side of the balloon. This will allow the students the opportunity to see if their predictions of how long the cups will stick are correct.

Using the information you have just gained from the previous activities, design an activity, I'm Hot - No I'm Not, where you can put a balloon on the 2 liter bottle and cause the balloon to expand and then contract down into the bottle. You cannot use heat from a hot plate or fire.

Help the students perform the experiment by leading them through the activity. Use questions to help the students discover the use of hot water to heat the 2 liter bottle. The students will immerse the bottle in the hot water container, and then observe the expansion of the balloon. Place a thermometer in the water and record the temperature. Take the string and measure the circumference of the balloon. The next thing they are to do is to cause the balloon to go inside the bottle without their assistance. Again use questioning to lead the students to discover taking the balloon off of the bottle, allowing the air in the balloon to escape, and then replacing it on the bottle. Ask how they could quickly cool the air in the bottle. Again, an option is to immerse the bottle in cold water. After they have done this, allow time for observation. Discuss with the students what has happened.

NOTE TO TEACHER: The air inside the bottle was heated and the molecules spread out filling up the balloon. When the balloon was removed, the amount of air that was inside the bottle became less. By replacing the balloon quickly, no air was allowed back inside. When the air was cooled it allowed room for more air in the bottle and the pressure inside the bottle became less than the pressure on the outside of the bottle causing the balloon to be pushed down inside the bottle.

The next activity, Suck it In, is one that would be safest as a demonstration by the teacher. Fill a small balloon with water and tie the end. Place the balloon on the mouth of a glass Ocean Spray jar. Ask the students if the balloon can be placed inside the jar. Their response will probably be to the negative. Tell the students what you are going to do and ask them to predict what will happen. Remove the water balloon. Light a piece of paper and drop it into the jar. Replace the balloon on the mouth of the jar while the fire is still burning. The fire will then go out and observe what happens next. Ask the students for an explanation. Ask the students how to remove the water balloon without breaking the jar. They will probably deem this impossible. Hold up a soda straw and ask if it would be a good tool in the removal. Take the straw and put it inside the jar between the balloon and the side of the jar. Take a hold of the neck of the balloon and it will come right out. Discuss why the balloon was so easy to remove using the straw.

NOTE TO TEACHER: The air is heated by the fire, and, therefore, rushes out of the open mouth of the jar. When the balloon is replaced on the jar the fire goes out and the air starts to cool. As the air cools, the air pressure inside the jar becomes less than the air pressure on the outside of the jar, causing the balloon to be pushed inside. When the straw was placed between the balloon and the side of the jar, the pressure equalized and the balloon could be removed quite easily.

Invite a magician to show ways they might use air pressure in his/her magic shows.

Invite a meteorologist to come to the class to discuss how high and low pressure affect the weather.

Invite a local fireman to your class to be interviewed by the students to see if there is ever a problem with the different pressures inside a burning house.

Language Arts: Write a story about how it would feel to be the balloon that was pushed into the bottle.

Write a cinquain about air pressure:
Line 1: one word title
Line 2: two words describing the title
Line 3: three words showing action
Line 4: four word sentence telling about the title
Line 5: one word (simile or metaphor for the title)

Environmental Studies: Explore the effects of air pressure.

Experiment with the force of air pressure. Thread a long piece of thin string through a straw. Tape or tie the string to objects a good distance apart and slide the straw to one end. Blow up a balloon and hold the neck closed. Roll a piece of tape and center it on the balloon. Tape the balloon to the straw. Release the balloon and watch what happens.

Master Teachers: Dennis Reule and Cindy Yocum