[MarkNY8679]

I am doing a organic chem lab where we are heating various samples in an oil bath to determine their melting point/range -- and am lost on the following questions:

1)What effect would poor circulation of the melting point bath (oil) have on the observed melting point?

2)If the melting point bath was heated too rapidly, an inaccuate melting point can occur, why?

3)What effect would the incomplete drying of a sample have on the melting point?

4)In this lab- samples are crushed into a fine powder and packed tightly into a capillary before being put into the melting point bath. Why must the samples be crushed to a fine powder, and why must they be tightly packed into the capillary-how does this affect the recorded melting point?

Can anyone help me answer these?? - For questions 1 and 2, I think that the melting point bath (oil) must be heated slowly to provide for even distribution of heat from the oil to the capillary. I am lost on question3. For question 4, I think the samples must be crushed finely and packed tightly to prevent air from gathering between the molecules and affecting the melting point. Thanks

[Yggdrasil]

For 1 & 2, you are correct.  You want everything in the bath to be at the same temeperature, so that the temperature you record in the bath is the same temperature as your sample.  Heating slowly and providing good circulation help the system reach thermal equilibrium.

For 3, if you don't dry your sample completely, you are introducing an impurity (water).  How do impurities affect melting point?

For 4, you are correct.  Air is a poor conductor of heat and can insulate parts of your sample from the surroundings, making your temperature readings inaccurate.