Hydrates:
(Hydrated and Anhydrous compounds)
Opal (SiO2)
Hydrates: •  Are solid crystals with trapped water molecules inside. -  The name of a hydrate consists of the compound name followed by the word hydrate with a prefix
indicating the number of water molecules.
Example  -
A Hydrate is written as the ionic salt and the number of water molecules associated with one compound.
-
Anhydrous compounds are formed when hydrates are heated and the water of hydration is driven off. Law of Definite Proportions:
•
Any given compound is always made of the same elements in the same propor7on by mass. “% by Mass” & “% Composi=on”. also called, Equation 
__________________________ ___________________ Percent(%) Composi=on: Is, how much mass each Element, adds to a Compounds total mass (as a %). (water) (Anhydrous)  Is the mass of each element (in a compound) divided by the mass of the en=re compound. __________________________________________________________________________________ Equa7on modified for Hydrates: _____Water______ X 100 Hydrated Compound = % Composi=on