Materials needed:

Book: Balloons Over Broadway by Melissa Sweet

Empty water or pop bottle (I used a glass one so that it could be used many times)

Baking soda


Funnel (for easily getting the baking soda into the balloon)

Regular sized (round) balloon

Balance scale, or digital scale (optional- to show the difference in mass of the two balloons)

Twisty balloons- one for each child (for making balloon hats) I prefilled mine in the interest of saving time.

Balloon hand pump (Definitely get one of these! Twisty balloons are nearly impossible to blow up without one.)

Time needed: 30-45 minutes  30-45-minutes-on-a-clock

Engage: Read the book, Balloons Over Broadway by Melissa Sweet. In order to get the book and activities done in 30 minutes, I paraphrased the story as I flipped through to show students the pictures. End the book by reading the last page: “Tony Sarg- the puppeteer who loved to figure out…” Emphasize to the students that with a little scientific thinking, problem-solving and perseverance, they too may create something that people with enjoy for generations.

Exploring and Explaining as we go: Get out the water bottle, vinegar, and baking soda. Tell students that in order to make the huge balloons float overhead, Tony Sarg put a special gas in the balloons that was lighter than air. Ask students if they remember the name of the gas (helium). Ask for examples of solids, liquids, and gases, and remind students of the properties of each. Solids: having a definite shape, being firm. Liquids:

Wet, like water, flowing freely and taking the shape of the container that it is in. Gases: clear, air-like substance flowing freely and filling up the container that it is in.

Tell students that you are going to mix a liquid with a solid, and make a chemical reaction that produces gas.

Pour the vinegar (roughly ½ cup to ¾ cup) in the bottle and ask if students know what it is. Ask them if vinegar is a solid, liquid, or gas.

Take a round balloon and attach the funnel to the mouth of the balloon. Get out the baking soda. Put about 4 teaspoons of baking soda in the balloon through the funnel.

Show students that the baking soda is a powder, and although it takes the shape of the container that it is in, this is only because the baking soda particles are very small, and there is a small amount of air in between each particle of baking soda (similar to the way dry sand will take the shape of the container it is in).

Tell students that you will tilt the balloon up so that the baking soda goes into the vinegar. Ask them what they think will happen before you do this. (Remind them that a chemical reaction will occur, and a gas will be made.) Ask them to guess what will happen to the balloon, encouraging creative thinking like, “maybe it will blow up!” I joke with them at this point and tell them all to run if it explodes. (But then, of course, I follow it up with, “Trust me, I’ve done this 100 times, and it’s only blown up once- just kidding.) 🙂

Dump the baking soda from the balloon into the bottle of vinegar, shake the bottle, and watch the balloon blow up with gas!

The gas being formed is carbon dioxide. Shake the balloon to let any fizzing liquid go back into the bottle, because if you are going to put the balloon on the scale later, you don’t want the liquid to interfere with the weight of the balloon.

Tell students that this gas formed is heavier than the air we breathe on Earth. Show them this by dropping the balloon to the ground. The balloon will fall with a “thud,” and it will be clear to students that it is heavier.

Take another round balloon and blow it up with the air in your lungs to appear the same size as the balloon with the carbon dioxide. Ask students to predict what will happen when you drop each of the balloons at the same time from the same height. (They may say that the one with the carbon dioxide will fall faster and harder, and this is great!) Ask them to explain the thinking to clarify understanding.

Drop both balloons at the same time from the same height and watch the one filled with carbon dioxide thump to the ground faster than the one with regular air!

Get out the balance scale. Tell students that you are going to put the balloon filled with CO2 on one side, and the regular air-filled balloon on the other. Ask them to predict what will happen. They should predict that the carbon dioxide-filled balloon will “go down further” than the balloon filled with regular air. Ask them to explain the thinking to clarify understanding.

Put the balloons on the scale so they can see that the carbon dioxide-filled balloon is heavier.

Switch the balloons just to prove that the scale is working.

Explain to students that although gases are clear, and we can’t always see their differences, this demonstration proves that these gases have different properties or characteristics. They may look the same, but when they are put in the same size containers, it is easy to see that one weighs more than the other.

Ideas for Elaborating Further (Optional):

Finish the lesson by handing out twisty balloons to the students, and taking them through how to make a question mark balloon hat! This further demonstrates that gas has mass and takes up space, as they will be moving the gas around in the balloon to the make the hat!

I chose a question mark to remind students that scientists ask questions, imagine, and solve problems.

Posted by Kim Angell, Children’s Assistant