How to grow Tin Crystals!


So this is basically what you need to
carry out this experiment: You need; a stannous chloride solution, a dish to hold it in, some alligator clips, some paper clips and a power source. Each of the paper clips will serve as an electrode, and they’re clamped to either side of the dish using the alligator
clips. The dishes then filled with a few
milliliters of two molar stannous chloride solution (~3 mL 2M SnCl₂) which I made in a
previous video. I’ll provide a link to the stannous chloride video in the
description. Then to the power source, an alligator
clip is attached to the positive and the negative terminals. The moment the
circuit is completed by connecting the second alligator clip, the crystals
should start to grow. The crystals will grow from whichever
alligator clip was attached to the negative terminal. So, after [it] was attached we can see the
crystal starting to grow. It was very interesting for me to see this the first
time but I was honestly quite underwhelmed at how slow it was and how
few crystals were growing. I was very underwhelmed with the results, so I decided that I’m going to need to use something with more current if I
want to get the crystals to grow faster and to get more of them. The crystals are pretty small, flaky and
fragile but if you like you can scoop them up and collect them. So I found an old power supply from a
laptop I used to have. I cut the end off and stripped away about an inch of the wire on the end. The free copper wire that you see
wrapped around the inner white wire is generally the negative or the ground. So it was removed from the white wire and twisted up a little. Then, with the white
wire free a little bit of it was stripped to expose the inner wire, which
is the positive. So now these are going to serve as our positive and negative terminals instead of the battery. And then just like before, we attach an
alligator clip to each of the terminals. In general, the wrapped wire is positive
but depending on the polarity of your adapter it could be negative. In the end, it doesn’t really matter because it doesn’t really matter which side the
crystals grow from. And then, to get things going we plug it in. So now when we use this much more
powerful power supply, we can see that the crystals are growing much faster
than before. However, due to the greatly increased power input it starts to heat up the solution and you can see that the solution on the red side starts to actually boil a little. So what’s happening here is known as a redox reaction. Basically, what happens is that the tin ions are oxidized at one end and reduced at another. So, the stannous chloride starts off as tin
2 plus (Sn²⁺) but at one side receives electrons and another it gives away [electrons]. At the positive side tin 2+ is giving
away 2 electrons to form tin 4+ (Sn⁴⁺) and at the negative side it’s receiving two electrons to form tin
0 or tin metal (Sn). Just for fun, you can reverse the terminals so the tin grows from the other side and you can see that the existing tin
crystals start to shrink. Because the solutions already been used
extensively and it’s pretty hot the demonstration isn’t the most
beautiful thing ever. But, in essence what we’re seeing here is the tin metal is giving up two electrons to form tin 2+ or tin 4+ which can
be re-dissolve in the solution. I opted to redo the experiment with
better lighting and indoors, and the result was much nicer. The crystals grew very nicely and I was quite satisfied with the result. To end the video I’ll
let this play out in real time. [music]

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