In this activity, learners will learn all about density differences, convection currents, and lift. We will make a rocket without rocket fuel! Think it’s not possible? Well, let’s find out!

Our tea bag is a thin piece of material that when you light it on fire it burns down and eventually flies up but why does that happen?

As the flame burns down the bag, it heats the air inside of the tea bag. The heat causes the air molecules to move quickly and spread out above the cylinder. These air molecules inside are much farther apart than those outside the cylinder. That means the air inside the cylinder is less dense than the air outside the cylinder. Warmer, less dense air rises above cooler, denser air. The flow of rising hot air inside the cylinder creates a convection current of air, generating an upward force called lift.

As the bag burns, it becomes both ash and smoke therefore losing its mass. Once the flame has burned to the bottom, the convection current provides enough force to lift the remaining ash into the sky.

Learning Time: 5-10 minutes
Prep Time: 5-10 minutes
Age Range: All Ages
Materials List: Tea bag (any flavor works), scissors, lighter, plate or pie pan, adult supervision
Keywords: Density, convection currents, lift, air pressure
Directions:

1. Gather your supplies! You will need a tea bag, scissors, a lighter, and of course adult supervision.

2. Head outside and find a table for this experiment.
3. Cut off the top of the tea bag. You do not need the label, string, or staples.

4. Empty the tea somewhere (extra points if you make a cup of tea with it!)

5. Now unfold the tea bag and straighten it out, you will want to open it like a cylinder.
6. Set it up straight on a plate or pie pan.

7. Now light the top of the bag on fire and step back to watch it take off!

Extensions

• If there are any remains, look at them closely to determine what’s in them.
• Try different types of teabags. Do they all work the same or do some burn up too much?
• Is this possible to do this with tissue paper?
• Is this possible to do with a roll of standard paper?