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Current time:0:00Total duration:8:45

Video transcript

in the last video we touch on the three states of matter that are really most familiar to our everyday experience the solid the liquid and the gas and I kind of hint that there is a fourth state which I don't cover because it's usually not the domain of an introductory chemistry course but a little bit of a discussion ensued on the message board for that video so I thought I would at least touch on that fourth stage and that's the plasma and I'll do it in a suitably bright color plasma and people consider it a fourth state because it has some properties of gases in some ways it's almost a subset of gases but it also has properties of conductivity that you normally wouldn't associate with with the gas what it is is and and you know just so you know when you fear sure you think oh you know that's that's a fairly exotic thing plasma and in the first video I say oh it only you know something that occurs at high temperatures which isn't exactly 100 percent right it doesn't have to be at high temperatures I really should have said now under extenuating circumstances where you have a very strong electromagnetic field or or something has to happen to essentially bump the the electrons or move the electrons off of gases that would have otherwise have kept their electrons so it's kind of analogous to what happens in metal when we talk about metal bonds we we talked about this notion of a sea of electrons where let's say if we talked about iron what happens with most metals is that they have so many kind of electrons and they're they're so willing to give them then the electrons just kind of float outside of outside of the atoms themselves and create this kind of big sea of electrons and then the atoms themselves become positively charged ions because they essentially donated some electrons to the sea so they're attracted to the sea and that's that's what makes them malleable and even more importantly what allows them to conduct electricity but they're all really packed closely together and it's a very dense structure a plasma is a situation where if you take gases and remember gases things are pretty far apart so you take a bunch of gases and they have high kinetic energy although they don't have to well it could be under it could be very low pressure but they're moving around and they're bumping into each other but they're not they're not close to each other they don't have fixed they don't have a fixed structure with each other or they're not rubbing against each other like in the case of a liquid but what happens in a plasma well one one situation is that you can you apply such a strong electromagnetic field that the electrons want to disassociate so let's say these electrons start bumping off of the plasma and so even this you know a solid has its own shape a plasma will take the shape of its container like a gas and sometimes it is described as an ionized gas and it's described as ionized because the electrons are bumped off and when the electrons are bumped off the otherwise neutral atoms now become now have positive charges and what this allows is essentially a conduction of electricity because now these electrons are free to move and you might say oh that sounds like a a bizarre state of matter where does it exist well probably closest to home it exists on enlightening enlightening and that's worthy of an entire video but the idea is is that you start having a huge potential difference between the clouds and the ground and the ground and then because you have this huge voltage difference between the two you have electrons that are essentially wanting to go into the ground right you have electron you have a buildup of electrons up here you have a buildup of electrons up here that want to go into the ground but they can't because air is normally a fairly fairly bad conductor it's an insulator but what happens is because there's so much electro potential here the electrons that are close in the molecules up here at least this is how I visualize it their electrons want to escape from these clouds because these clouds are starting to get so their electrons start to want to move away in the air molecules whether you're talking about it you know the air is a mixture of oxygen and nitrogen and carbon dioxide they start wanting to get away from the clouds so they start disassociating and start forming like this this ionized air and eventually at some point this happens to such agree that you can actually get conduction from the cloud to the ground and that conduction is is when the air is in a plasma state so it's happening at a you know the conduction allows extremely high temperatures and the electrons to flow all the way to the ground the other common example that you might see something like this or well actually not like this but at least a plasma state is in stars and that's because you have extremely strong electromagnetic fields extremely high pressure and that type of an environment once again and you know this I'm super oversimplifying it you can get to a state where the electrons can get disassociated from things that otherwise wouldn't want to give up their electrons so I thought I would touch on that because it's an interesting subject and it it exists in the universe it's actually on a universal level because stars are pretty much all plasma it is actually the most common state of matter in the universe although in our everyday life we probably encounter solids liquids and gases a lot more now one other thing I want to maybe clarify from the last videos I talked about the bonding between water molecules and let's say we're talking in the solid state so if I have oxygen and have a hydrogen a hydrogen and then I have some electrons here some electrons here and let's say there's another say there's a hydrogen here and an oxygen and a hydrogen maybe there's an oxygen here but that has a hydrogen I'm just you know whoops I don't want to do that so these are and then this has a hydrogen and then it has two electrons on two electron pairs so I talked about the notion and and then we talked about it many times before that oxygen is so much more electronegative that it hogs the electrons and so the oxygen side starts to have a partial negative charge while the hydrogen side start to have a partial positive side because when the hydrogen is essentially all of its electrons are hanging out close to you like close to the oxygen it's electron hydrogen ends up just becoming like this proton that's floating out there because we even said it doesn't even have neutrons in most cases so as a slightly positive charge this will have a positive charge and the positive and the positive polar end of the of the water molecule is attracted to the negative polar end and I called it polar but I really should have called it it shows you my memory from high school chemistry is not ideal I really should have called it hydrogen bonds and hydrogen bonds so this is a hydrogen bond or this is a hydrogen bond it's usually it's just a matter of the name I use but I just want to clarify that because that is what's typically used in your chemistry class I don't want to confuse you and that is just the bond that exists from a a partially positive hydrogen atom because it's its electrons are hanging out near the near the oxygen and a partially negative oxygen atom in the water molecule because all of its it's stolen all of these these electrons from the hydrogen you draw it like that it's called a hydrogen bond and hydrogen hydrogen bonds tend to form between hydrogen and well really only a handful of super electronegative atoms and that's nitrogen fluorine and oxygen and that these are actually the three most electronegative atoms so when the nitrogen a nitrogen if you you know nh3 when it bonds with hydrogen when it bonds with hydrogen it essentially is so electronegative that you have the same situation all the electrons hang out here so you have a partial negative charge partial positive on the hydrogen's same thing with hydrogen hydrogen hydro hydrogen fluorine you get the same HF you get the same type of hydrogen bonds and so in this case these guys would want to be would be attract to the nitrogen part of other molecules or in form hydrogen bonds so I just want to get that out of the way and with that done I think we can return to some of the ideas of the last video and actually do some problems so in the last video we saw that let's take the case with water let me draw good actually let me just state the problem first so let's say that we have a let's say that we have