Lithium in wekipedia?
Lithium has only about half the specific gravity of water, giving solid metal lithium sticks the odd heft of a light/medium wood, such as pine. The metal floats highly in hydrocarbons due to its low density, and jars of lithium in the laboratory are typically composed of black-coated sticks held down in hydrocarbon mechanically by the lid of the jar and other sticks.
Answer:
The hydrocarbon (that's just mineral oil) is intended to cover the lithium so that it is not exposed directly to air. The problem is that lithium floats on oil, so you have to keep it pushed down inside the oil. That is what this passage is talking about.
pine means "the wood of a pine tree".
A hydrocarbon is a molecule composed exclusively of carbon and hydrogen: carbon atoms for a chain in the middle, and hydgrogen atoms bond along the edges. This diagram should work:
h h h h h h
h c c c c c c h
h h h h h h
That's an example of a hydrocarbon, I think it should be called hexane or hectane.
Hydrocarbons are almost entirely nonreactive, because the covalent bonds are almost fully nonpolar (C and H have electron affinities of 2.4 and 2.1). Lithium is highly reactive (all the alkali metals are) because it only has one electron in its valence shell. Water is also very reactive, so lithium can't be stored in water. It needs to be kept in a nonreactive substance, like hydrocarbonic oil, until it gets used for whatever.
Lithium burns in water, so it needs to be stored in an oil, some sort of like mineral oil that won't burn.
All they mean by hydrocarbon is oil, in the general sense.
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