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Current time:0:00Total duration:9:13

Video transcript

let's talk a little bit about chemical reactions and chemical reactions are a very big deal without chemical reactions you or I would not exist in your body right now there are countless chemical reactions going on every second without chemical reactions we would have no life we would not even have the the universe as we know it so what are chemical reactions well there any time that you have bonds being formed or broken between atoms or molecules so what do we what do we what are we talking about there well this is maybe one of the most fundamental chemical reactions once again if this one never occurred we'd be in trouble we would not have we would not have any water but let's think about what it is actually describing so over here on the left hand side we have the reactants let me write that down so here we have the reactants these are the molecules that are going to react and then we have an arrow that moves us to the product so let me do that in a different color so we have an arrow that moves us to the product or though we could say the products and so what are the reactants here well we have molecular hydrogen and we have molecular oxygen now why did I say molecular hydrogen because molecular hydrogen which is the state that you would typically find hydrogen and if you just have it by itself is actually made up of two hydrogen atoms you see it right over here one two hydrogen atoms and what we have in order to have this reaction you don't just need one molecular hydrogen in one or one molecule of hydrogen one molecule of oxygen for every four for this reaction to happen you actually have two molecules of molecular hydrogen so this is actually made up of four hydrogen atoms so let me make this clear so this right over here this is two molecules of molecular hydrogen and that's why we have the two right out front of the H sub 2 the this little subscript 2 tells us there's two of the hydrogen atoms in this molecule and then this big this big white two that we have right over here that tells us that we're dealing with two of those molecules for this reaction happened that we need two of these molecules for every for every molecule of our oxygen and molecular oxygen once again this is composed of two oxygen atoms one two so under the right conditions so you need a little bit of energy to make this happen if under the right conditions these two things are going to react it actually it's very very reactive molecular hydrogen molecular oxygen so much so that it's actually used for rocket fuel you are going to produce two molecules of water we see that right over here and look I did not create or destroy any atoms I had one I had one I had one oxygen atom here it was part of the oxygen molecule right right here and then I have the second one right over here now now they are part of separate molecules I had I had a I had one two three four hydrogen's I now have one two three four hydrogen's just like that and actually this produces a so we could say some energy and I'm being inexact right over here some energy and then we could say a lot of energy a lot of energy so this is a reaction that you just give it a little bit of a kickstart and it really wants to happen a lot a lot of energy so one thing that you might wonder and this is something that I first wondered when I learned about reactions well how do how does this happen oh this is a very organized thing you know do these do these molecules somehow know to react with each other and the answer is no chemistry is a incredibly messy thing you have these things bouncing around they have energy they they're bouncing around all over the place and why should when you provide energy they're going to bounce around even more rigorously enough so that they they collide in the right ways so that they break their old bonds and then they form these new bonds so whenever you see these reactions in biology or chemistry class keep that in mind it looks all neat and organized but in a real system these are these are all of these things just bouncing around in all different crazy ways and that's why energy is an important thing here because the more energy you apply to the system the more that they're going to bounce around the more that they're going to interact with each other the more reactants you put in the more chance that they're going to bounce round and be able to react with each other now I'm going to introduce another word that you're going to see in chemistry a lot this this water these two we see we have two water molecules here we could call them molecules but since they are actually made up of two or more different elements we could also call this a compound so water water is you could call it a molecule or you could call it a compound so this is a molecule or compound while this molecular hydrogen you would not call this a compound and this molecular oxygen of course it's a molecule but you would not call it a compound either and just to get an appreciation of how much energy this produces let me show you this picture right over here that's the space shuttle and this this big tank right over here let me this big tank contains a bunch of liquid oxygen and hydrogen and to create this incredible this incredible amount of energy it actually just you-you-you mix the two together with a little bit of a with a little bit energy and then you produce a ton of energy that makes that makes the rocket that makes the Space Shuttle well space shuttles been discontinued now but back when they did it to make it to make it get-get it's it's necessary it's necessary velocity now let's talk about the idea so you know this this reaction strongly goes in this in the direction of going to water but it can actually go the other way but it's very very hard for it to go the other way so in general we would consider this to be an irreversible reaction even though it is you know irreversible sounds like hey you can't go the other way it just really means that it's very unlikely to go the other way you have to supply a lot of energy to go the other way to make this reaction go the other way you would have to do something called electrolysis you're providing energy etc etc but in general the way that this is written because the arrow is only pointing in one direction this is implying that it is irreversible irreversible irreversible which probably makes you think well what about reversible reactions and I have a I have an example of a reversible reaction right over here I have a I have one bicarbonate ion and the word I on that's just to use to describe any molecule or atom that has either has an imbalance of electrons or protons that cause it to have a net charge so this makes this anion and actually right over here this is a hydrogen this is a hydrogen ion right over here both of these are charged one has a positive charge one has a negative charge but they are both they are both ions and this reaction right over here you have the bicarbonate ion that looks something like this this is just my my hand drawing of it reacting with a hydrogen ion it's really a hydrogen atom that has lost its electron so some people would even say this is a this is a proton right over here this is an equilibrium reaction where it can form carbonic acid and notice all that's happening is this hydrogen is attaching to one of the oxygens over here and this is in equilibrium because if it in an actual and an actual solution it's going back and forth if you actually provide more reactants you're going to go more in that direction if you provide more of the products over here then you're going to go you're going to go in that direction and so in an actual if in an actual environment in an actual system it's constantly going back and forth between these two things and different reversible reactions might tend to one side or the other if you provide more more of the stuff on one side it's might go in more than the other direction because these are going to they're going to be more likely to interact or if you provide more of this it might go in the other direction because these because these might more likely react with their surroundings or disassociate in some way now just to get a sense of you know it's nice to kind of you know are these just some random letters that I wrote here cabrón ik acid is actually an incredibly important molecule or we could call it a compound because it's made up of two or two or more elements in living systems and in fact you know even even even in the environment and even when you go out to get some fast food when you have carbonated drinks it has carbonic acid in it that disassociates into carbon dioxide and that carbon dioxide is what you see bubbling up carbonic acid is incredibly important in how your body deals with excess excess carbon dioxide in its bloodstream carbonic acid is involved in in the oceans taking up carbon dioxide from the atmosphere so when you're studying chemistry especially in the context of biology these aren't just you know interesting things that seem very academic these are affecting your real life and your body and your environment
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