Red Flags
Never place a plastic bag in your mouth or over your head!

Questions to Ask
Ask the children to compare the bag before and after it has been inflated. Does the blown-up bag remind them of something else? What shape is it now? How did the book move? What’s another way of lifting the book? Which way is more fun? What can be seen in the bag after you’ve blown into it? How did it get there?

Science Connection
Our exhaled breath has water vapor in it. Some vapor stays in the passages in our noses; some goes out into the air around us. When our moist breath enters the bag, the water molecules condense on the inside of the bag. (Camels have long, twisted nasal passages, so most of their water vapor stays inside their noses. That’s one reason why camels can go without drinking for long periods of time.) Air takes up space, can hold things up and make things move. Air pressure all around us is quite strong, but you’re used to it so you really don’t notice it. In fact at this moment, the air pressure pushing down on you is about equal to the weight of an automobile! On average the atmospheric (air) pressure on Earth is 14.7 pounds per square inch. That means that every square inch of your body, the top bottom and sides of a table, the walls of your house, etc. has 14.7 pounds of air pressure pushing on it.

To explore the amazing things air can do To observe the water vapor present in our exhaled breath.

What You Need

  • Book
  • Drinking straw
  • Zip top sandwich bag

    What to Do
    Place the straw halfway in the bag. Zip the bag tightly around the straw. Blow into the straw. At this point, give the children time to explore inflating and deflating the bag. Deflate the bag. Now, with the straw locked in, place the bag on the edge of a table with the straw facing you. Place a book on top of the bag. Blow into the straw again. What happens to the book?

    What Happens
    The book will be lifted by the inflated bag.

    Air: The invisible mixture of gases that surrounds us and our planet earth.
    Condensation: The process of vapor or gas changing into a liquid.
    Lift: Occurrence when air pressure under an object is greater than the pressure on top of the object. The air is able to hold the book up and give it support.
    Lungs: Sponge-like organs in our chest cavity which give oxygen to our blood and remove carbon dioxide from it.
    Pressure: The force exerted against an object.
    Water vapor: Gaseous state of water below its boiling point. It occurs when water is in the form of mist.
    Work: Effect or action produced by natural forces.

    Try This
    Try placing the deflated sandwich bag in the middle of a telephone book. What do the children think will happen if they blow in the bag? Look around the house for other things you can lift with air.

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