Everyone who has gone through High School Chemistry has seen the “Sodium In Water” experiment. First the periodic table is explained, and the reactivity of the Alkaline and Alkaline Earth Metals is talked about, along with their counterparts; the Halogens. A small chunk of Barium, Magnesium, Calcium, Lithium, Sodium and Potassium is than dropped in water, one after the other, and their reactivity is observed as the metals first bubble, than sizzle, melt, and finally catch fire, as is the case of Potassium. The luckier ones amongst us may also have watched the video “Periodic Table” (I think that is the title. Its one where some idiot sings the names of all the elements in the end) where Rubidium and Cesium are also dropped, with vastly more impressive results.
That they don’t tell you in High School though, is what would happen if you were to take one of the more reactive metals, such as Sodium, and drop it into water at very large quantities.
PowerLabs, always at the forefront of science, brings you the answer to that age old question.
One reasonably sized chunk of sodium, and an outdoors water puddle surrounded by nothing valuable or flammable.
Here is a typical Sodium sample that was used for the experiments. Sodium was obtained at the price of 24 dollars per 25 grams at the time. The sample pictured weights under 10 grams (density of Sodium = .97g/cc).
Sodium reacts with water to form Sodium Hydroxide and Hydrogen Gas. The reaction produces a lot of heat, which is sufficient to melt the metal (MP: 96C) if enough of it is used. If the reaction is scaled up further, the molten metal may start to boil, which is when exciting things start to happen: The boiling metal breaks apart and thus increases its surface area, speeding up the reaction rate. The faster reaction produces more heat, which ignites the Hydrogen Gas being produced, which leads to an explosion, which breaks up the remaining liquid metal, which leads to an extremely rapid reaction that results in so much heat that the metal catches fire. The final explosion probably releases as much energy from combusting Hydrogen as it does from burning sodium (2Na + O2 = 2NaO).
The picture to the left shows the culminating point of a video done outdoors during a storm. The sodium is seen first being removed from the bottle, than thrown outside on a water puddle. The metal reacts with water melting and boiling, and than a small explosion occurs which sends up molten sodium drops into the air. As soon as the drops hits the water puddle again a large explosion ensues, which sends sparks flying up into the air and leaves a large smoke cloud behind. Very good video, a must see. Clicking on the picture will download the video (3.5MB, MPG).
This video shows a larger chunk of sodium being thrown in the same parking lot at night. The fence seeing in the background is about 10 meters high, and the sparks are flying above it (286Kb, MPG).
Other Experiments (Not documented):
1- Sugar Cube sized chunk of Sodium dropped into a half filled Cola Can: The can explodes and is ripped to shreads.
2- Sodium Dropped into 68% Nitric Acid: The sodium reacts violently, forming a intense flame as the Hydrogen combusts with the NO2 / N2O4 formed by the decomposing acid. After a few seconds the reaction escalates into an explosion and acid is sprayed out of the reaction vessel. This is definitely one I am not repeating!