|MadSci Network: Chemistry|
Hi David, When sodium metal reacts with water, the following reaction is taking place: 2Na(s) + 2H2O(l) ---> 2Na+(aq) + 2OH-(aq) + H2(g) + energy Most of the energy of the reaction is released as heat. The hydrogen gas is flammable and the reaction is hot enough to ignite the hydrogen upon contact with oxygen (air). That is the source of the fire that occurs during the reaction. Sodium metal melts at 97.8C (approx. the boiling point of water) and has a density of 0.968 which is less than the density of water. So, the reaction produces enough heat to melt the sodium before it has completely reacted and the ball (or droplet) of melted sodium then floats on the surface of the water until it has completely reacted. This is the "clear, colorless sphere" you saw. In fact, the sphere is neither clear, nor colorless. It is just highly reflective because the imperfections of the mottled grey surface of solid sodium have been melted away. _Safety Note_: Reacting sodium metal with anything is very dangerous! Neither normal fire extinguishers nor most chemical fire extinguishers will adequately extinguish an alkali metal fire. In fact some will make it worse! (CO2 also reacts with sodium though not as violently as water does) Be sure to have a big bucket of sand around when using sodium because it is the safest way to extinguish a sodium fire. Hope this info was helpful. Jeremy.
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