This movie shows lithium reacting with water. We see that
lithium is next to helium in the periodic table (it follows
helium). Lithiums proximity to a noble gas provides a useful
connection to its reactivity. In general those elements closes to
the noble gases are amoung the most reactive. When the sample of
lithium is dropped into the water we see a reaction occurs
because bubbles are formed. We talked about these bubbles in
class. We wondered what the gas was. The only substances
initially are lithium and water. So the gas has to be something
with the elements Li, H or O. We know both hydrogen and oxygen
are gases. We do not know whether compounds containing lithium
can be gases. (HINT: Anytime a metal
reacts with another substance the compound produced which has the
metal will not be in the gas phase.) So we can only conclude the
gas is either hydrogen or oxygen. Turns out the gas is hydrogen.
We'll learn later this semester how to tell whether the gas is
hydrogen or oxygen by a simple experiment.