Chromatography and fractional distillation can be used to separate compounds.
In which type of separation is a thermometer needed for checking that complete separation has occurred?
the answer is fractional distillation of two liquids of different colours
if my answer is wrong please check it
Your answer probably is the intended correct answer but i don't like the way the question is asked/stated.
In particular I don't like the part I'm showing in bold face type.
"In which type of separation is a thermometer needed for checking that complete separation has occurred?
First, not all liquids can be separated by fractional distillation and second, the thermometer will not tell you anything about how complete the separation is.