The baking powder cannon

The napkin is soaked in the vinegar and the baking soda begins to react with the vinegar. The cork is pushed out of the bottle with a swing. The bottle rolls on the pencils in the opposite direction to that in which the cork flies.

Vinegar is poured into the bottle so that it covers the bottom when the bottle is lying down, but does not flow out. The still open bottle with the vinegar is placed on some round pencils, which act as rollers. Then pour baking soda into the unfolded napkin (about a third to half a sachet is enough) and close the napkin again. (For thick napkins, cut the napkins in half.) Now push the packet of napkins with the baking soda into the bottle so that it floats in the vinegar. Close the cork quickly, but not tightly! Many plastic bottles like the one shown above are corrugated and therefore do not roll. In this case, place a piece of cardboard or another suitable lightweight base on top of the rollers. In the experiment shown here, a polystyrene plate of the type used for sliced cheese was used.

• 1 plastic bottle with an easy-to-seal cork (preferably a rubber stopper),
• vinegar,
• Baking powder, round pencils or similar,
• possibly a piece of sturdy cardboard or a thin sheet of polystyrene 1 napkin (not shown),

Sometimes it takes a while for the cork to come out. With flexible plastic bottles in particular, sufficient pressure is only built up after a certain amount of time.

What is technically behind the experiment

In this experiment, the principle of recoil can be clearly seen. After the napkin is soaked with vinegar, the baking soda in the napkin reacts with the vinegar. This produces carbon dioxide. The pressure in the bottle increases and the cork is pushed outwards and flies away. When part of the mass of a body is thrown away, a recoil occurs. The object with the remaining mass always moves in the opposite direction to the propelled mass. This principle can also be explained by the law of conservation of momentum, which states that the total momentum of a system always remains the same. The lighter the body that is pushed back, the more clearly the recoil can be seen.

What the experiment has to do with everyday life

The principle of recoil can often be found in everyday life and in nature, for example in rocket propulsion, the recoil when shooting a rifle, or even in an octopus that moves according to this principle.

Marion Thölert & Nicole Taebi