Copper Sulfate (slow motion) – Periodic Table of Videos

Copper Sulfate (slow motion) – Periodic Table of Videos


now I’ve seen this reaction lots of times but this is the first time I’ve seen it in high speed where we pour the solution in quite slowly but then watch what happens the reaction of copper with ammonia is quite a well-known reaction and often students school children come across it quite early on in their career it’s a reaction which gives both a precipitate and then a color change it involves copper sulfate which in solution is a fairly pale blue and you can imagine in the solution you have copper iron Cu 2 plus surrounded by six water molecules further too close together and to that a rather further apart this does not absorb light very strongly so the solution looks very pale when you add ammonia which is alkaline in when it’s dissolved in water you precipitate a pale blue solid which is a mixture of copper hydroxide and copper sulphate so called basic salt and then as you add more ammonia this Reda’s all’s to give a very intense blue color the blue color is due to copper ions the same copper ions but now with for ammonia molecules interacting with it in the tetrahedral shape this is a baby toy that I got in Italy it’s quite fun so there aren’t really jewels and cheese attached to it no no no this is just this pizza as well so when the copper goes from this shape that is quite pale colored to this one that is tetrahedral the color comes much more intense and it is a very nice demonstration for people just beginning chemistry to see how copper can form the so called coordination complexes where stable molecule like ammonia can actually bind to the copper ions and what I find quite surprising is if you watch carefully it really goes blue dark blue before you see the precipitate whereas chemically it should be the other way around you should see the precipitate and then the dark blue color and my only explanation and this may well be wrong is that it takes time for the precipitate to form crystals that are big enough you to see when crystallites are very small their size is shorter than the wavelength of light so they appear invisible though they can still absorb light and then as they grow bigger you see physical clumps of them because they’re much bigger than the wavelength of light and this growing of particles can be relatively slow compared to the initial precipitation which forms really tiny ones when you look at at the end it looks rather beautiful it looks very like the planet Earth seen from space you you

100 Comments

  1. A little annoying that the slow motion video was very much out of focus (if you look closely at the end around 4:04, the focal plane is about where the edge of the wooden stand is, at the bottom edge of the video). Would love to have seen the reaction in high-detail.

    Thanks for the video anyways though πŸ™‚

  2. As ever an interesting explanation. Perhaps you could take it further and demonstrate and explain the amazing property of cuprammonium hydroxide in dissolving cellulose.

  3. It doesn't neccesarily turn dark blue.
    It depends on the concentration of the reactants, the amount you pour in, and the rate of addition. Concentrated ammonia, if added quickly in small amounts, will quickly create a gunk of precipitate. Large amount will quickly create a complex cation, turning everything dark blue quite fast.
    Diluted reactants take more time to react.
    There's a balance between the complex tetraamminecopper(II) and the precipitate, and the final look depends on few factors.

  4. Do you realize you guys have been doing this for half a decade, I'm shocked you guys have not celebrated it because it's such a huge accomplishment.

  5. I was always taught that 5 molecules of water surround Cu2+ in CuSO4 (water of crystallisation). So it's actually 6.

  6. I need to get some ammonia now. I've had some copper sulphate for a good while and never seen this reaction yet! I've merely only ever done methanol green flames, copper plating, and a small study, extrapolating data from the 1940's and 50's to determine the density of a copper sulphate aqueous solution, given the amount of copper sulphate dissolved in water.
    A surprisingly linear graph, showing that for ever 1.0 mols of CuSO4 dissolved into 1L of solution, the specific gravity will rise by 0.10

  7. I love how the high-speed footage sheds new light on well-known reactions like these for even the professor. And how he draws up an explanation so quickly. It's amazing!

  8. And while i'm here, other sources suggest square pyramidal for the tetraamino monohydrate in solid form; not tetrahedral. Seems unlikely that the aqueous solution would contain unhydrated tetraamine complex…?

  9. You've made them quite digestible for those of us in the US, as well. When posted your video from within the BoE, you were kind enough to put the USD value along with the GBP value. Your attention to detail is appreciated! Also, yes, I'm sharing all of your channels.

  10. Another really cool reaction is adding some HCl to the copper ammonia solution. All the precipitates dissolve and the solution becomes clear again with some smoke coming from the top of the test tube. I'd love to see that through a high speed camera. Love your videos. Salutations from the US! πŸ™‚

  11. Would the deeper blue color possibly be more predominant as a result of the rapidly reacting "surface" of the copper cloud concealing the rest of the stuff, which hasn't touched any ammonia yet? Then the precipitate would become visible later, when the fluids are thoroughly intermixed, because there's not enough free ammonia for it to react with as rapidly as the first phase.

  12. Woah woah woah woah.
    Brady Haran films these?
    As in, the guy that brings me my beloved Numberphile videos also is the reason I can see Einstein's ghost lecture me on chem online?
    Mr. Haran, thank you very very much!

  13. I wish I had my chemistry teacher same as you, would have gladly taken career as a Chemist Researcher rather than electronics engineering.

  14. I hope one day you will get a camera person who knows how to frame. You can include the face and the models at the same time. Framing to get the top of his hair and less than half of the models is not educational — It is just frustrating.

  15. I would love to see the same reaction on a flat surface. That would make the reaction 2D and easier for the camera to focus on. Higher magnification would bring out more detail as well.

    Beautiful reaction, though. Makes me wish off taken chemistry in school rather than comp sci.

  16. I would be very interesting in the chemistry about origins of life. There has been another breakthrough lately. COULD YOU EXPLAIN WHY SINGLE ELECTRON TRANSFER IS SO POWERFUL? nature.com/nchem/journal/v5/n6/full/nchem.1649.html

  17. I was about to do this at work but when I looked up the MSDS for it I saw that copper sulfate is toxic to the environment, so I didn't do it. I could have easily used 5 grams (about a pinch of salt) but still didn't want to do something that I didn't have to. My point is, always look up an MSDS of chemicals to know what you are handling, how to dispose of it, and always wear proper PPE.

  18. when you get copper sulfate it is a solid, once you place it in water it fully dissociates to copper and sulfate ions and most likely doesn't get used in the reaction to form the precipitate

  19. When I was a kid, sulfur used to be spelled sulphur and sulfates would be sulphates. Has the IUPAC nomenclature changed since then?

  20. The solution is made of copper sulfate. What happens is that the dissociated copper ions form hydrated complexes (that's what he's talking about at 1:07) which are then involved into the reaction with ammonia. The sulfate ions play no role in the reaction(s) hence why it was disregarded.

  21. I have a question about Helium. Can Helium be frozen, I ask this because Helium is so close to absolute zero when liquid, but can it be solid?

  22. Yes it can, but you need a very high pressure and a temperature close to zero Kelvin. The "official" melting point of Helium is at 0.95 K at a pressure of ~2.5 MPa.

  23. Yes. IUPAC standardized on sulfur (not sulphur), caesium (not cesium) and aluminium (though it accepts aluminum as an alternative) in 1990.

  24. From thenakedscientists
    At atmospheric pressure, all known materials would become solid at absolute zero with the exception of one; helium. Pressures around 25 atmospheres or above must be added to helium in order to freeze it or else you'll just end up with a superfluid at cryogenic temperatures. Air becomes solid quite a bit above absolute zero.

  25. Then how would the do it, if they need more air pressure but all other gasses turn solid at that point. They would have to use some other way that doesn't need air.

  26. Imagine a box completely full of liquid helium at 0K. Now imagine you push the sides of the box in. You just increased pressure on the liquid helium and at 25atm (~368PSI) you will have solid helium forming. Pressure on the helium doesn't require air pressure, just the container providing pressure on the helium. CO2 is a liquid at room temp if you compress it a bit. That's how fire extingishers and paintball tanks work. They're liquid inside, and gas when you release the pressure.

  27. I love how the professor jumps from describing the tetrahedral shape of the ammonia molecules to saying that the baby toy is quite fun. Mr. Poliakoff is the best.

  28. A slight pedantic note: The hydrated copper complex should be [Cu(H2O)4]2+ and appears as a distorted tetrahedron due to the Jahn-Teller effect. Otherwise a brilliant video, makes me happy to have read chemistry at University.

  29. I just went down to the hardware store so I could see this at home with my own eyes. Don't take my word for it, but it was probably the most beautiful reaction I have ever seen. It really is truly awe inspiring.

  30. I had a thought on why the color change came before the precipitation of the CuOH. The hydrated complex had an octohedral electronic configuration, which seemed to have little absorbance of visible light. The ammonia-copper complex has a tetrahedral configuration, which implies some shifting of the electronic configuration which might only be possible by forming copper ions. Thus, the CuOH precipitate may only form once the electrons shift, which would happen slower than the color change.

  31. I heard that Ice can be formed by pressure too. Maybe if you had a container of liquid helium deep enough the weight of the helium would crush the bottom layers into solid helium, but it would have to be very deep because helium is very light. Is there a video that has solid helium in it?

  32. @5thDragonDreamCaster – I don't know about Helium, but Hydrogen has a melting point nearly that low. On Jupiter, fluctuations in temperature and pressure, combined with the much stronger gravity on Jupiter, have been known to change lakes of hydrogen into immense pieces of metal hydrogen for short periods. Helium should do the same thing, but with even more pressure.

  33. Didn't you say that this was copper sulfate? Your reaction shows only copper hydrate without showing any sulfate. What happens to the sulfate in the reaction?

  34. So could we see this at full speed? Those of us who were the victims of the California State Public Education System missed out on cool stuff like this (since we were too busy studying things like … well, like a bunch of crap that I didn't like. Best thing that ever happened to me was getting out of high school. THAT'S when the learning started).

  35. Why does the complex ion , (the one causing the dark blue solution), only forms when the ammonia is added in excess? Doesn't aqueous ammonia already have a large amount of ammonia already? Thanks

  36. Dear doctor, would you please take consideration for this comment.
    Let me tell you that in french :
    "Je suis professeur agrΓ©gΓ© en physique appliquΓ©e" (don't know how to translate this)
    And as a physicist who likes chemistry, I want to tell you that I totally agree with your explanation of "blue coming out before precipitate". (starts at 2:52)
    I'm pretty sure you've got the right answer to this question. Cheers from France. I love your videos (and ties…)

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