cooling curve octadecan-1-ol

Cooling curve of octadecan-1-ol個experiment點解??
Through the experiment, as we mark the temperature change and plot a graph, we can obtain a cooling curve similar to the below figure.


圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701101060130913873437080.jpg


In the cooling curve there is a part (AB in the figure) with no temperature change, and that part is the time that octadecan-1-ol solidify, so, we can know that the change of state does not involve temperature change of substances, that is there is no kinetic energy change in the particles of octadecan-1-ol during solidification.

Actucally, this experiment is used to carry out the concept of latent heat.
I guess it will be mentioned later, in the experiment, the part of the cooling curve with no temperature change(AB in the figure) is the substance releasing latent heat of fusion, I think this will also be mention afterwards.

I suppose you aredoing an experiment on investigating the melting point of the substance octadecan-1-ol by plotting a cooling curve.

octadecan-1-ol has a melting point at around 60 degrees Celsius. As such, you should observe a plateau on the cooling curve, the temperature at which such plateau occurs gives the melting point of the substance.

The appearance of a plateau on cooling is explained by the principle by when a substance undergoes a state change, e.g. from liquid to soild, latent heat is given out. The decrease of internal energy of molecules in the substance is accommodated by the decrease of potential energy of molecules, but not by the kinetic energy. Hence, there is no temperature change during the change of state.