Why does Copper Sulfate turn white once it has lost all its 5 waters, and blue when it is hydrated?

Question

I did an experiment recently that invloved evaporating water from 55 ml of Copper Sulfate Solution so that solid copper sulfate remained. When all the water has been evaporated, blue copper sulfate crystals remained. However, the copper sulfate crystals were heated a little too long, and they turned white. Why do copper sulfate crystals turn white when they loses waters? Why do they turn blue when hydrated? If you could provide any other information or website links regarding this topic, feel free! Thank you!

Answer 1

Copper II Sulfate pentahydrate as you said is blue,
Copper II Sulfate tetramine monohydrate is a deep violet,
and Copper II Sulfate is a grayish white. Why you ask; it has to do with the ligands (water and ammonia amongst other things) that bond to the central atom and cause a different crystal structure. When light is reflected and refracted through the different structures different electron excitments occur providing the color observed.

A way to think of it is with ice cubes, if they take a long time to form they result in clear ice (much like that which is sculpted) however if the ice forms quickly it is very cloudy. This happens because the crystal structure of the ice is different in the two examples, the slow formed had a long chance to get well organized while the short time batch was just frozen in place without the opportunity to organize.

Answer 2

It is basically due to the electronic structure of the hydrated copper ion compared to the anhydrous form. When the copper ion is complexed with water molecules, the orbital arrangements of the ion's electrons is different than in the free copper ion.

Here is a website that talks a little about coordination complexes:
http://www.bookrags.com/Complex_(chemistry)

Answer 3

There is a explanation to this in the Crystal Field Theory of complex salts which explains the colour to many substances including CuSO4. It states that the d-orbitals of the Cu(+2) ions are of the same energy level when they are left alone in void. However when you supply a ligand - like water, these energy levels develop a small difference. Now electrons in the level that has a lesser amount of energy can absorb a certain wavelength of light photons and get excited to the next level, momentarily. When they return, they re-emit that photon, giving colour that you see. So when you remove the water by heating, it is back to its original self with all the d-orbitals at the same level. So you miss the colour.

Answer 4

It is because of the d-electrons undergoing orbital transition. This occurs when copper sulphate datively bonds with water. No transition ocurs when there is no dative covalent bonds.
Just read more because this is the small I learned in high school.
Note: This phenomenom is for the transition elements solely except the first and the last in the series.

Answer 5

cos hydrated cu undergoe what is called transition temperature @ 36deg.hydrated cu is blue due 2 bcu itself bein blue.but anhydrous cu is whith even dougth it has cu is bcos of is molecular dissolution in water at d initials.remember dat cu bein blue in water ia a test 4 d presence of water.

Answer 6

why the sky is blue?!