Final answer:
To determine if a sample is a pure single substance, compare its melting point to the expected melting points of known pure substances.
Step-by-step explanation:
A pure substance is a material that is not a mixture and includes elements and compounds. Impure substances have a temperature range over which they melt or boil, whereas pure substances have a sharply defined melting or boiling point.
To determine whether each melting point observation corresponds to a pure sample of a single substance, we need to compare the observed melting points to the expected melting points of known pure substances.
If the observed melting points match the expected melting points, it indicates a pure sample of a single substance.