hi there my name is Chris Harris and I'm from alerts.com and welcome to this video on enthropy change definitions so in this video we're just going to look uh just briefly at the different types of enthropy changes that you need to know for the born Hab cycle U and this is applied to ionic compounds only um so what I'm going to do is I'm just going to go through the all the different types of eny change the exact definitions that you need to know and uh just some examples as well and let you know whether they are endothermic or exothermic with a reason as well so we're just going to start with um these different types of enthropy changes now they happen uh all the time in reactions for various reasons it maybe because of Bond's being broken or electrons are being moved from one place to another or because water is effectively breaking up an ionic compound and surrounding it so we're getting a hydration enthropy so it's going to go through all these different types with the symbols uh and just give you an example like I say so we're going to start with enthalpy of formation now the enthropy formation is when one mole of a compound is formed from its elements in standard States under standard conditions it's really important that it's one mole of a substance and you can see here we've got the formation of water H2 O2 both of them in their standard States H forming one mole of a substance it can't have a two in front of there or half it's got to be one mole this process is exothermic it gives out heat energy because we're Bond forming okay next one enthropy of atomizing now this is the eny change when one mole of gous atoms are formed from an element in its standard States so you can see here we've got um uh one mole of uh sodium being formed in its in a gaseous form and this is sodium in its standard state which is a solid uh and here I've got another example which this is half cl2 uh and this is forming chlorine gas now this sometimes is known as a a bond enthalpy um so You' got to be careful and just check with the exam board um but some exam boards accept that as atomization now because we are turning something from a solid into a gas we have to put energy into that so we describe it as endothermic that's why I put the en en there okay enthropy of first ionization energy so this is the energy change or the enthropy change when one mole of gasius ions are formed from one mole of Gus atoms so effectively we're removing one electron from it so this is sodium in the gous state the state symbol is really really important we form in sodium which is a gas as well plus an electron because we're having to put energy in to do this to remove the electron this is an endothermic process uh the second ionization energy is the same it's endothermic except removing an electron from something that's already positively charged we're forming a ca2 plus ion plus an electron okay and this is endothermic so the next one is electron affinity now if you affinitize something it means you are attracted to it so this is the enthropy change when one mole of Gus one minus ions are made from one mole of Gus atoms so we are forming we're starting from an example here is chlorine gas it's in the gaseous State and we're forming uh adding an electron to this and that will form CL minus gas so this is an exothermic reaction because we are adding an electron to a neutral atom so energy is normally given out because we're affiniti an electron now this is really different to the second electron affinity and you got to be really careful with this especially when you're drawing born Hab cycles and this is the entropy change where one mole of gasius 2 minus ions are made from one mole of Gus one minus ions very similar to the one down here except we're forming two minus now the only difference is is that this one's actually endothermic you got to be really careful for this so I've given an example for oxygen o minus which is in the gas State plus an electron will form O2 minus the reason why this is endothermic we need to put energy in to do this process is because we're trying to affinitize a negative electron to a negative ion you've got you've got obviously repulsion there repulsive forces so you need to put energy in to overcome that to form your O2 minus gas okay next one is lce formation this is the empty be change in one B of solid ionic compound is formed from its gaseous ions again this is really important state symbols are so important in these so you got sodium gas chlorine gas in the ionic form forming sodium chloride solid this is an exothermic reaction because we're Bond forming okay next one enthropy of hydration so this is the enthropy change when one mole of aquous ions is formed from one mole of gaseous ions so here's our gasas ions here and we're forming aquous ions uh this is an exothermic process because water is effectively forming interactions with your uh negative ions so we class that as Bond forming so it's an exothermic process enthalpy of solution now this one depends on the type of compounds that we're forming uh that we're dissolving Sor but this is the enthropy change in one mole of solute a solute is a solid uh was dissolved in enough solvent which could be water for example uh so that no further enthropy change occurs on further dilution so effectively we're trying to dilute the whole thing and there's no more uh solute left so this is going from KCl solid to KCl Aquis uh this can be exothermic or endothermic and it depends on the type of chemical that you're using so for example sodium hydroxide is an exothermic reaction where we dissolve it water whereas something like potassium chloride is slightly endothermic so this can change and the last one is the Lattis dissociation eny um and this is basically the eny change when one mole of ionic compound separates into its gaseous ions so here it is here NAC solid plus na+ gas and cl minus gas this is an endothermic process because we are separating the NAC it solid form into two irons so energy needs to be put in to do that now um that's all the definitions it is there's loads of them there you do need to remember these definitions uh and you do need to see them applied as well so uh I have done a video on the born ha cycle where really this is where you learn a lot of it uh and if you just check my uh playlist um then you can find out the born her cycle and how to work it out and how these are actually applied but that's it hope that helps bye