a tea bag (I used Earl Grey)
a room without a draft
Because of the potential fire hazard, this demonstration should be performed by the instructor, not the students.
The tea bag will lift off almost vertically; however, if there are any drafts in the room it will change the path the rocket will take. Therefore, this experiment should be performed away from flammable materials, and students should be seated at an appropriate distance away from the experiment.
This cool experiment is a fun after dinner experiment with the family. Your guest won’t believe their eyes as the Rocket shoots to the ceiling.
1) Take your tea bag out of its container, and look for a small staple that connects the paper or string to the actual bag.
2) Carefully pull back the staple and remove it from the bag or cut the string.
3) Unfold the tea bag and empty out the tea leaves.
4) Put your finger in the middle of the cylinder.
5) Place the cylindrical tea bag upright on a plate.
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, count down 5,4,3,2,1 BLAST OFF!
HOW DOES IT WORK?
There are three principles acting on the cylinder you’ve made from the bag of tea that make this experiment work.
The first principle involves the density of the air within the cylinder as it compares to the air on the outside of the cylinder. As the flame burns down the bag of tea, it heats the air that is contained within the cylinder. The heat excites individual air molecules and causes them to move more quickly and spread out within the cylinder. The excited air molecules inside the cylinder are farther apart than those on the outside of the cylinder, making the air inside the cylinder less dense than the air outside the cylinder. This warmer, less dense air rises above the cooler, more dense air.
This experiment also demonstrates the principle of convection currents. As we just explained, the burning bag of tea creates hot, less dense air. This creates a thermal, or convection, current. The space created by the less dense air inside the cylinder allows the dense air outside to push upwards from the bottom. That movement or current of air is referred to as a convection current.
But that isn’t enough to create the rocket that you saw at the end of the experiment. As the bag of tea burns, it turns into both ash and smoke. The smoke lifts away and dissipates into the air, leaving just a delicate ash frame. Since the ash is so lightweight, the force of the rising hot air is strong enough to lift the ash into the air.