Analyzing Blue Vitriol Discussion Fill in the blanks on your handout!

Did you synthesize the Blue Vitriol? Maybe? Maybe not? If you got the original bright blue color of your original sample of blue vitriol then you were on the right track!

What is Blue Vitriol used for? Control mold & fungus Control algal growth in water Dye fixative Fertilizer Blue/green flame for fireworks

Remember: Inputs and Outputs Inputs: substances added to a system, a reactant Outputs: substances that are produced from a system, products

Was heating blue vitriol an example of a chemical reaction or a physical change? Both 1 st it was physical change B/c it changed texture (from blue crystal  light blue powder) only changed physical form 2 nd it was chemical reaction B/c as it was heated longer, color of powder changed from light blue  white/gray; COLOR CHANGE = CHEMICAL REACTION!

Other evidence for a chemical reaction When you synthesize BV by adding water you get a NEW color Clear water + gray/white powder  dark blue solution! When you add water to solid gray/white powder, heat is released Water + solid  heat released! Exothermic reaction!

Blue Vitriol aka Copper Sulfate pentahydrate CuSO 4 5H 2 O Naturally occurring hydrate Hydrate: material or compound that has a specific number of water molecules attached to it Water can be removed from material by heating it When water is removed the material is anhydrous Heat CuSO 4 5H 2 O and you get anhydrous CuSO 4

Blue vitriol contin’d Anhydrous materials: do not contain water, BUT CAN absorb water from their surroundings Ex: desiccants (drying agents) Ex: “do not eat” packets - made of silica gel Ex: dehumidifying agents in sachets - keep things dry Hygroscopic: = “water seeking” Takes up and holds onto water

Blue Vitriol contin’d Hygroscopic materials: absorb water, usually water from atmosphere, A hygroscopic material is a hydrate! The water can USUALLY be removed from the material by heating. Ex CaCl 2, MgSO 4, Na 2 SO 4 This is an example of REVERSIBLE chemical reaction MOST chem. Changes are nonreversible. Absorbing/removing water is a reversible chemical reaction that can go back and forth!

Hygroscopic example BaCl 2 +2H 2 O  BaCl 2 2H 2 O

Blue Vitriol contin’d Anhydrides: materials that react with water and the reaction is IRREVERSIBLE! Anhydrides react w/ water and form NEW COMPOUNDS (acids & bases) Ex: BaO + H 2 O --> Ba(OH) 2