Identify that pure substances have distinct measurable properties (e.g. melting and boiling point, reactivity, strength, density) and mixtures have properties dependent on the identity and relative amounts of the substances that make them up.

A student measures the boiling point of two colourless liquids, sample X and sample Y. Sample X boils at 78.4 °C every time it is heated. Sample Y begins boiling at 82 °C and continues to boil as the temperature rises to 95 °C. Identify which sample is a pure substance and which is a mixture. Justify your answer.

Which property would best identify a substance as pure rather than a mixture?

Which of the following is a characteristic property that distinguishes a pure substance from a mixture?