Chemistry

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Video

Materials

• 1 tea bag - Note that there are some tea bags that are not suitable for this demonstration, namely those that burn up completely and those that are "glued" together in their middle.
• 1 porcelain plate (or other non-flammable surface)
• Matchbox or lighter
• 1 pair of scissors
• Safety equipment: 1 fire extinguisher

Explanation

This simple demonstration is actually about both chemistry and physics. Knowledge of chemistry is needed to explain what happens when the tea bag burns, while knowledge of physics is needed to explain why it flies.

When the tea bag burns, the tea bag reacts with oxygen in the air. In this chemical reaction, the tea bag and the oxygen are consumed, at the same time as, among other things, carbon dioxide and water are formed. However, the entire tea bag doesn't burn up. Some of the less flammable ingredients remain as a porous and light material.

To explain why the tea bag flies, we move on to physics. When the tea bag burns, the air inside the tea bag tube heats up. This means that the molecules the air consists of (oxygen molecules, nitrogen molecules etc.) move more and more. This leads to them colliding with each other and ending up further apart. The air inside the tea bag tube thus has a lower density than the surrounding air - in simpler words, it becomes lighter. Warm and light air rises, as Earth's gravity has a weaker gravitational pull on it compared to cold and heavy air. Since some air around the tea bag tube has also been heated, and the whole rocket is thus surrounded by hot air, it joins this air mass as it rises.

In Sweden, this demonstration is called a "norwegian rocket" - a humorous wink to their neighboring country's.

Experiment

You can turn this demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• What happens if you light the tea bag somewhere else?
• What happens if you tape several "tea bag tubes" together into a long rocket?

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