Enthalpy

... may have also happened on the smaller alcohols it will not have been as severe as the activation energy for the combustion of the alcohols as they get smaller decreases. This can be explained by looking back to when I examined the bond energies, the smaller alcohol's needed less energy to break the bonds in the reactants and so less energy is needed to initiate the reaction. The results that I got from my experiments for butan-1-ol will have been affected in two ways *Firstly carbon is a better insulator than copper, it has a lower thermal conductivity value and so it will stop as much heat getting through to heat the water as there should be

*Secondly the carbon has come from the spirit burner and for my results I am assuming that all the alcohol that leaves the spirit burner is combusting and releasing heat to contribute to the heating of the water which it is quiet clearly not. This will mean I am assuming that more alcohol is needed than really is to cause the increase in temperature.

Apart from the butan-1-ol my results are as expected showing a clear increase in the energy released per unit mass of alcohol.

So that it is possible for me to see which alcohol has the highest enthalpy of combustion I need to find which alcohol releases the most energy per mole. From the measurements I have taken I have the temperature increase per gram. If you raise the temperature of an object you increase the energy of the particles it is made from, to do this you need to supply energy. The energy needed to raise the temperature is proportional to the mass of the substance and the temperature rise Energy µ mass x temp increase

The constant of proportionality depends on the substance you are heating, it is called the specific heat capacity. Energy = specific heat capacity x mass x temp increase (j) (J/g/ oc) (g) (oc)

The results that I am going to use are Alcohol Initial Temperature Final Temperature +/- Mass of Alcohol Burnt Methanol 27oc 49oc 22oc 1.12g

First I need to find the heat exchanged to the water Specific heat Capacity of water,4.2 Mass of water heated,100g Heat energy exchanged = Mass x Specific Heat x Temperature To the water (g) Capacity Rise (J) (J/g/ oc) (oc) = 100 x 4.2 x 22 = 9240J 9240J is the heat energy taken in during the experiment, this needs to be converted to heat taken in per mole of alcohol burned

1.12g Methanol 9240J 1 g " 9240J/1.12 32g " 9240J/1.12 x 32 26400Jmole-1 So there is 264000 J released from 32g which is one mole, to change to KJ simply divide by 1000 Which gives 264kJmole-1

There is also heat absorbed by the calorimeter that I can also work out Specific heat capacity of copper, 0.385 Mass of calorimeter 61.55g Heat energy exchanged = Mass x Specific Heat x Temperature To the copper (g) Capacity Rise (J) (J/g/ oc) (oc)

= 66.55 x 0.385 ...