Exam 1 Flashcards
what is a physical property
it is a way to distinguish a sample without changing its chemical composition
what is the melting point
it is the point of phase change from a solid to a liquid, all the heat goes into the phase change so there is no broad temperature change
what does heat do to the crystalline lattice in a solid when near the melting point
it disrupts the lattice and allows the phase to change
how do IMFs determine physical states
weak IMFS (dip dip) usually result in gaseous compounds while strong IMFs are more likely to be solid
why is melting point a misnomer? how do we record itl
it is a misnomer because it is actually a range, the first number is the first drop of liquid, the last number is the temperature at clear
what indicates a pure compound in MP
a sharp melting point over 1-2°C
what are the 4 abnormal forms of melting point
decomposition: solid turns black without liquefying over a sharp range
Sublimation: solid turns to gas without liquid
Polymorph: different forms of crystalline lattice with different mps
hydrates: anhydrous forms of the solid will have different mps than hydrated forms
what is the effect of impurities on melting point
impurities depress and broaden the melting point
what is a eutectic mixture
it is a precise mixture of components that melts over a sharp range that is lower than both of the individual mp values
how can you use mixed melting points to identify a compound
if the mixed melting point is low and broad, it is not the same
if the mixed melting point remains the same as the known, it is the same
why do you grind the sample in a melting point experiment
to ensure even heat distribution
why can you not overpack a capillary tube
if it is too full, it will take more heat to melt the whole sample
it may overextend the apparatus and may cause uneven heat distribution
what happens if the temperature setting is on 10°C/min rather than 1°C/min for a melting point
it broadens the melting point, if the temperature is too high the temperature reading will increase before the sample has time to melt fully
