 So what we can now do is calculate what's called the molar enthalpy of combustion. And this allows us to make direct comparisons not only with or between different alcohols but also between the value that we've gained experimentally and the value that we might expect to find theoretically if we looked it up. So in this case what we have is to calculate the molar mass of ethanol. And again we use our periodic table to do that. So we need to write down the formula C2H5OH. It's sort of the way we write down ethanol. So that's two carbons, six hydrogens and one oxygen. When you put those together you end up with a value of around 46. So in this case all I'll do is just multiply my 6.2 kJ per gram by 46.068 I think is the exact value. And that will give me a number that is around 285.2 kJ per mol. Now that's nice as a number but what does it mean? Well it only means something if we do two things with it. Firstly we compare this number to other alcohols. Have you got methanol? Have you got propan-1ol, propan-2ol? Have you got butan-1ol, butan-2ol? Have you got methyl butan-2ol to compare between primary, secondary and tertiary alcohols? It will depend what you have as to what you use. But the other thing we can do is we can compare our experimental or empirical value with a theoretical value. If I look up theoretical value for the molar enthalpy of ethanol I find that that value is actually 1 about 1360 kJ per mol. You can see this value is significantly higher than this one. That's telling me that I may have some questions about my validity in this particular experiment. And in fact there are a couple of factors that may have affected that particular value. Obviously any energy loss is going to be very significant. So as the ethanol is combusting, if it's hitting the air, if it's hitting any other objects, it's going to transfer some of that energy to those other objects or to the air. And we know that heat radiates. It doesn't just go in a single direction, it radiates in all directions. So some of that energy is going to be lost. It's not all going to go into heating the water. And that's our assumption is all of the energy from combustion is being used to heat the water. The other thing that could actually affect this too is whether or not the type of combustion is complete or incomplete. If you find that you're generating a lot of carbon as soot, for example, then that's an indication that we have incomplete combustion that is insufficient oxygen for this combustion reaction to occur. And if that's the case, then obviously we're not going to be able to generate the high enough amounts of energy that we would expect if we were able to provide sufficient oxygen for complete combustion. That is likewise going to affect our value and again in the same sort of direction. So energy loss is going to mean we're not going to collect as much energy as we would expect, so that's going to drop our value. Incomplete combustion may also mean that we have less energy than we would otherwise have for complete combustion. So combined together, these sorts of things can significantly lower the value that we expect to get theoretically when we do it experimentally. This is a great experiment to give you a look at concepts like validity, reliability, thinking about your controls, thinking about the factors that can affect the value that you collect in your experiments, and definitely worth exploring a few different alcohols in order to compare the molar enthalpy of combustion for a range of different alcohols. And thanks for watching.