Tea Bag Rocket(Teresa Glass)

Author

Teresa Glass

Principle(s) Illustrated

Convection Currents
Newtons Laws
Volume and Pressure

Standards

- - - - HS-PS2-1.
      - HS-PS3-2.

- - - - Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. [Clarification Statement: Examples of data could include tables or graphs of position or velocity as a function of time for objects subject to a net unbalanced force, such as a falling object, an object rolling down a ramp, or a moving object being pulled by a constant force.] [Assessment Boundary: Assessment is limited to one-dimensional motion and to macroscopic objects moving at non-relativistic speeds.]
      - Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative positions of particles (objects). [Clarification Statement: Examples of phenomena at the macroscopic scale could include the conversion of kinetic energy to thermal energy, the energy stored due to position of an object above the earth, and the energy stored between two electrically-charged plates. Examples of models could include diagrams, drawings, descriptions, and computer simulations.]

Questioning Script

Prior knowledge & experience:

How fires works, potential and kinetic energy, how air affect force

Root question:

What pushes the Tea-Bag into the air?.

Target response:

As the flame burns down the cylinder, it heats the air inside of the tea bag. When air's temperature increases, so does its volume

Common Misconceptions:

The fire burn the paper and makes the rocket take off. The rocket simply disappears into the air.

Procedure

What You Need

One tea bag (Some brands work better than others. We used Bigelow tea; Lipton tea bags don't work as well).
A flame source (either a lighter or matches)
A non-flammable "launch pad"
Adult supervision

What to Do

1.Take your tea bag out of its container, and look for a small staple that connects the paper and string to the actual bag.

2. Carefully pull back the staple and remove it from the bag

3. Unfold the tea bag over a trash can and empty out the tea leaves. Once emptied, your tea bag should be able to lie flat on a surface.

4. Rub the material until you can turn the tea bag into a cylinder.

5. Place the cylindrical tea bag upright on a non-flammable surface such as ceramic plate or granite countertop. Don't light the tea bag on fire when it's on top of something flammable like paper.

6. With adult supervision, light the top of the tea bag on fire and let the flame work its own way down the teabag. Make sure you light the TOP of the tea bag.

7. Sit back, and watch it take off!

What’s Going On?

As the flame burns down the cylinder, it heats the air inside of the tea bag. When air's temperature increases, so does its volume. Consequently, if the mass of air stays the same but the volume increases, the pressure will have to decrease, making the air less dense. Faster moving air molecules in the hot air will rise and the cooler air will settle beneath them. This flow of rising hot air within the cylinder creates a convection current of air, generating an upward force.

At the same time, the tea bag's mass keeps decreasing as it burns, and the ashen skeleton that remains is much less massive than the original tea bag. Once the flame has burned to the bottom, the convection current provides enough force to lift the remaining ash into the sky.

Photographs and Movies

A Photograph of the tools used in this experiment is found on this link:Tools for Tea Bag Rocket Experiment

References

Fiery Tea Bag Rockets http://www.physicscentral.com/experiment/physicsathome/teabagrockets.cfm

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