in this video we're going to talk about the chemistry of electroplating which is a really common technique used for metals and it just happens to be one of my favorite topics in all of chemistry so in simple terms I'd say that electroplating is a process where you usually take an object made of one type of metal and you cover it with a thin layer of another type of metal okay and let me tell you electr plating is often just called plating for short okay so electr plating or plating is used for many purposes but one of the most common uses is to make inexpensive jewelry if you see something like a gold necklace or a silver ring and it's selling for real cheap it was probably electroplated pieces of jewelry like these aren't made of solid gold or solid silver instead they're made of a cheap metal like copper or zinc and then electr plating is used to put a thin coating of gold or silver onto the surface that's how the jewelry can be so cheap because it's mostly made of an inexpensive metal and you only need a tiny amount of the really expensive precious metal to just coat the surface so that cheap metal so let's talk through the chemistry of electroplating let's say we have a copper ring and we want to Plate it with a thin silver coating here's how we do it so we'd start with a copper ring and a piece of solid silver what we want to do is we want to get some of the silver atoms to come off this piece of silver and transfer them over onto the surface of this copper ring so the first thing we're going to do is put these two objects in liquid here's a liquid now this liquid is water with some chemicals dissolved in we'll talk more about it later but for now I'm just going to call this liquid the solution but just putting the silver and the copper ring in the solution isn't enough to start the plating process and that's because electroplating is a type of electrolysis which means that we have to use electricity to cause a chemical change here the chemical change is putting some silver atoms on the surface of this copper ring so here's what we're going to do we'll pull out some wires and hook these two objects up to a battery these are the wires there's a battery now check out which side of the battery these objects are connected to and that's important we hook this silver piece up to the positive side of the battery which means that the battery is going to be trying to pull electrons out of the silver and electrons are going to be moving Through the Wire in this direction towards a battery and then the copper here is going to be connected to the negative side of the battery which means that the electrons are going to be moving out of the battery into the copper ring the be moving along the wire in this direction so that's our setup and we can call this an electroplating cell which just means a device that you use for electroplating so that's the big picture of the electroplating cell now I want to talk about how this actually works right how we can get silver atoms off this piece of silver and transfer them onto the surface of the copper ring in order to understand that we got to use our Atomic Vision to zoom in millions and millions of times so we can see the atoms and the electrons that make up the silver piece that make up the copper ring and that make up the solution so here is a magnified view of the piece of silver and the copper ring these circles here are the atoms AG is the chemical symbol for silver and CU is the chemical symbol for copper and these sections here are right on the edge of the pieces of metal so here for this silver piece I'm imagining that this magnified section is right here so everything to the left is the piece of silver but then everything to the right is the solution now these two objects are way closer in my magnified view than they are in real life but I want to make sure that we can see both of them and then over here on the copper ring I'm magnifying this section right here on the left side so everything going here onto the right is in the ring and everything on the left is in the solution okay so remember what our goal here is we want to move some of the atoms from the piece of silver onto the surface of the copper ring how are we going to do this well here's how we're going to move them by changing their charge okay this is one of the most important rules in electrochemistry that neutral atoms make up solid metal and you can see that all of these atoms here are neutral they're just AG they don't have a charge but on the other hand metal ions can usually dissolve in water okay so if we can change the charge of these neutral silver atoms and if we can turn them into ions we can get them to dissolve off the piece of solid silver and move into the solution all right that is the job of the battery that's why we've hooked it up to the battery okay remember that there's this wire at the top of the piece of silver leading to the positive side of the battery which means that electrons are being pulled to the battery in this direction so here's what's going to happen I'll take this silver atom as an example okay what's going to happen is one of its electrons is going to get pulled out by the battery okay and so it's going to move through the metal up in this direction to the battery this silver atom lost one of its electrons so that means that it's now going to have a positive charge it used to be neutral AG but now it's AG 1+ so now it's an ion and it's no longer going to be part of this solid metal instead it's going to float away from the solid piece of silver and move into the solution and this is all because we changed the charge we changed it from neutral to plus one let's see that happen again we'll take this guy pull out one of the electrons this electron moves up to the battery since this atom just lost one of its electrons it's now going to become ag1 plus and it's going to move out into solution coming away from the solid piece of silver this silver atom right here loses one of its electrons up to the battery and it becomes another ag1 plus okay so now we have these three silver ions that have entered the solution and they've come apart from the piece of metal now sometimes in drawings of electrochemical cells like this people will actually change the shape of the silver to show that pieces of it are coming off so I'll actually do that here just in case you run into a diagram like this in your textbook see what I've done is I've I've made the edges Jagged instead of smooth to show that chunks of the silver are actually coming off as the atoms get turned into ions okay so now we have ions that are dissolved in into solution that have come off the piece of silver now the next thing I want to do is I want to get them stuck to the surface of this copper ring here so how am I going to do that well we're going to do the same thing that we did here we're going to change their charge okay keep this rule in mind neutral atoms make up solid metal metal ions can usually dissolve in water so right now these dissolved silver ions are floating around but if we could turn them back into neutral atoms over here we could get them to start making solid silver on the surface of the copper ring now what are we going to have to do to change these from ag+ into AG neutral well since I have a positive charge we'll need to add one electron to each of them and that is what this battery is for remember the battery is trying to pump electrons down into the copper ring so here's this here electrons are being pushed from the battery down in this Direction let me just move this over here a little bit there we go electrons are being pushed into the Copper from the battery so let's look at what would happen okay here comes an electron down from the battery through the copper now this Ron is negative and the silver ions are positive so they're going to begin to attract and this electron is going to go into the silver and now the silver has gained an electron so it no longer is positively charged and it turns in to neutral silver and it sticks to the surface of the copper ring it starts to form solid silver right it's no longer dissolved in water it's gone from 1 plus to neutral so it's now solid silver okay the same thing is going to happen with another one of these electrons it comes down from the battery into the copper it goes into the silver ion the silver ion loses its charge because it's gained an electron and Bam it's neutral silver and it's turned into solid silver on the surface of the copper one more because I just think this is so cool one more electron down from the battery sh into the silver ion turns it into a neutral silver atom and as you can see we're building this surface this very thin surface or coating of solid silver on the outside of the copper ring so sometimes if I were drawing this in a diagram I might show this with something like this to indicate that the copper ring looks like it's turning into silver it's just getting this this uh layer of silver atoms on the top of it okay so that's the piece of silver and that's the copper ring the last thing that I want to talk about is the solution okay now this electroplating process won't just happen in regular pure water you've got to dissolve some chemicals into the water to allow electroplating to happen and if you're electroplating silver a really common chemical to dissolve is called silver nitrate that's what you dissolve in the water to make the solution now silver nitrate is an ionic compound it's made of two things it's made of ag1 plus and it's made of the nitrate polyatomic ion 1 plus one minus and when silver nitrate dissolves in water the ag1 plus and the no 3 1 minus come apart okay here's another one they'd be stuck together and then they come apart just like this so by dissolving the silver nitrate into water to make the solution we get these positively and negatively charged ions floating around here these ions have a number of jobs okay first you can imagine that adding more AG pluses is a good thing because these can then move over here and turn into solid silver on the surface of the copper ring the negative nitrate ions are important because their negative charge balances out the positive charge of the silver ions that are coming into the solution from the piece of silver and we always want charges to balance okay but the most important job of the positive and negative ions is that they act as electrolytes which means they allow electricity to flow through this solution they complete the circuit and they allow the battery to work okay so the battery can then pull electrons here and push them into here okay so that's why the solution is important but I don't want you to worry too much about it all I want you to keep in mind is it's just important to dissolve an ionic compound in water in order to make a solution that electroplating isn't going to happen in just pure water so now that we've talked about the silver the solution and the copper ring let's just look at this whole process one more time okay we go over here to the piece of silver one of its electrons is pulled out by the battery okay this turns it from a neutral silver atom into a silver ion it floats out here into solution and then it comes over here to the copper ring where an electron is moving down from the battery the electron goes into that silver 1l ion the silver loses its charge and becomes solid neutral silver on the surface here of the copper ring okay so now that we've looked at how this process of electroplating works I want to talk a little bit more about how we can describe this using terms of oxidation reduction anodes and cathodes so let's take a look at that