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Unit 12: Alternative Energy Page 26 of 31
bag containing the water and the The bag containing water and the
Epsom salt that was not heated hydrated Epsom salt feels cool.
feel warm or cool after shaking? When dehydrated Epsom salt is
Does the bag containing the water mixed with water, heat is given off.
and the Epsom salt that was When hydrated Epsom salt is
heated feel warm or cool after mixed with water, heat is
shaking? absorbed. When something gives
off heat it feels warm, while
something that absorbs heat feels
Discussion cool.
Epsom salt is a hydrate of the salt Energy is required to remove
called magnesium sulfate. A individual ions from a salt crystal.
hydrate is a chemical substance However, energy is given off when
containing water combined with the individual ions that break away
another chemical substance from the crystal become
(usually a salt). The water surrounded by water molecules
molecules in a hydrate are called that are dissolving the salt. If more
waters of hydration. They can energy is required to remove
usually be removed from the individual ions from a salt crystal
hydrate by heating. The process of than is given off when the ions
removing water from a hydrate is become surrounded by water, then
called dehydration. the salt solution becomes cold. If
In this experiment, when you more energy is given off when the
heated the Epsom salt in the oven, ions become surrounded by water
you removed most of the water than is needed to remove
molecules (waters of hydration) in individual ions from a salt crystal,
the salt. then the salt solution becomes
warm.
A salt is made of positive and
negative ions. Ions are charged When hydrated Epsom salt
atoms or groups of atoms. In dissolves in water, more energy is
Epsom salt, magnesium i n r required to remove the magnesium
positive and sulfate ions are and sulfate ions (and the waters of
negative. The waters of hydration hydration) from the crystals than is
surround these ions in Epsom salt. given off when the magnesium and
sulfate ions become surrounded by
You should find that the bag
containing water and the the dissolving water molecules.
dehydrated Epsom salt feels warm.
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