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Homework Help: Question on Hydrated Molecules

  1. Nov 15, 2006 #1
    Hey, Im a gr11 student and I just did a lab, and I do NOT understand a thing.

    Ok, so I have hydrated Copper (II) sulfate, and basically I heated it up in a test tube in order to make it an anhydrous copper (II) sulfate compound

    My question is:

    -Is this a chemical or physical change?

    I am seriously lost here, since the ionic compound (Copper II Sulfate) didnt change, and just the water, so I thought it was a physical change. It could also be reverted easily to the original hydrated compound, by just adding a few drops of water. On the other hand, gas was formed, and there was a change in color..... so... Im really lost..yeah.. lol
    Last edited: Nov 15, 2006
  2. jcsd
  3. Nov 15, 2006 #2


    User Avatar

    Staff: Mentor

    You are on the best track to understand that classifying all changes as either chemical or physical is a crap :wink:
  4. Nov 15, 2006 #3
    i'm with borek. its very annoying to classify some things especially when it could be both.

    on one hand, it could be a chemical change since each unit of CuSO4.xH2O is losing its water and becoming just CuSO4, and you release water vapor in the reaction.

    on the other hand, hydrated salts aren't really different from regular salts, since the water isn't actually a part of the core molecule. It's just a regular salt molecule with a water molecule "stuck" to it that just sort of tags along. Heating unsticks the water molecule and removes it as a gas particle. I think the evidence here is stronger for a physical change. IMHO at least.
  5. Nov 15, 2006 #4
    plus, correct me if im wrong experts, but i dont think there is much of a reactivity difference with anhydrous and hydrated salts, except in cases where the water can interfere to give different products. I think theres just a difference in the reaction times? This is even more ammo for physical change rather than chemical change.
  6. Nov 15, 2006 #5
    Thanks, your input was really helpful =)

    I handed in my lab and I'm trying not to think about it. :rofl:
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