![]() Potassium nitrate is one of the components of gunpowder. Potassium salts are used as fertilisers, such as potassium chloride - which used to be called chloride of potash. Sodium salts are essential to life – ordinary table salt is sodium chloride. It is also used as a heat transfer agent in some types of nuclear reactor. Sodium (vapour) is used in bright yellow street lights. Some of its compounds are used as mood stabilising drugs. Lithium is used to make rechargeable batteries and lightweight alloys. The reaction of alkali metals with water is pretty vigorous and as we see in the video clip as we go down Group 1 of the Periodic Table, from Lithium to Caesium, things get more and more frightening. One of the signature reactions of alkali metals is their reaction with water to form alkaline solutions, for example sodium reacts with water to form sodium hydroxide – caustic soda. They do not occur naturally because they react readily with air and moisture and so need to be stored under oil. They are in fact very soft metals that can be cut with a knife and have relatively low melting temperatures. They are grouped together because they all behave similarly (except with different ferocity) and together form Group 1 of the Periodic Table. The alkali metals are the elements Lithium, Sodium, Potassium, Rubidium, Caesium and Francium. This time we've put a safety screen between us and the reaction.You can see that things gradually become more terrifying as we go down the group. The heat given out by the reaction is produced so quickly that the Hydrogen gas catches fire, it burns with a lilac flame. All the alkali metals react with water in the same way. Now for Sodium, the same sort of thing happens, although the reaction is a bit more vigorous. ![]() The metal floats on the water and reacts with it, giving off Hydrogen gas. Now let's see another reaction of the alkali metals, the reaction with water.
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