Question:
Hello! I am an Earth Science- student teacher. I have
prepared an activity for my students in which they grow crystals of alum,
salt and sugar at different temperatures (one sample is cooled at room
temperature, the other in a fridge). The point is to demonstrate the
effect of cooling temperature on crystal formation and relate this to the
differences between extrusive and intrusive igneous rocks. I am designing
an answer key to some questions, but I need your opinion on the answer to
the following:
What are some important similarities and differences between this type of
crystal formation (ie. in the lab, alum and sugar crystals) and the manner
in which crystals in igneous rocks form?
Replies:
Alum, common table salt and sugar crystals are formed by the evaporation
of water in a saturated aqueous solution of each. In contrast, igneous rock
is formed by the crystallization of molten rock under high temperature and
pressure. That is quite different.
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