Melting vs Burning
Why wont your finger melt in a fire?
Your finger is made up of very complicated molecules all connected
together by chemical bonds. So are plants and other animals. These
molecules cannot be separated from one another. Specific chemical
substances, for example water, can be in three common forms solid, liquid,
and vapor. In the solid the molecules are held in place, called a crystal,
when the temperature gets high enough -- and this depends upon what the
substance is -- the molecules can "jiggle around" enough that they can
move past one another fairly easily. This is the liquid state and the
temperature where that happens is called the melting point. At an even
higher temperature the molecules "jiggle around" even more and they can be
"bounced" into a gas -- called the vapor. Very complicated molecules can't
behave like this because they are all connected together.
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Update: June 2012