Question

distinguishing mixtures from pure substances through physical properties
read the descriptions below of two substances and an experiment on each. decide whether the result of the experiment tells you the substance is a pure substance or a mixture, if you can.

• sample a is 100. ml of a clear liquid. the density of the liquid is measured, and turns out to be 0.77 g/ml. the liquid is then cooled in the refrigerator. at 10.0 °c two separate clear layers form in the liquid. when the temperature is raised back to room temperature, the layers disappear.
• sample b is a solid yellow cube with a total mass of 50.0 g. the cube is put into a pressure chamber and the pressure raised by pumping in nitrogen gas. at a pressure of 55. atm an orange liquid is observed seeping from the cube. after 30 minutes this flow stops, and the smaller and lighter - colored cube sits in a puddle of orange liquid without further change.

is sample a made from a pure substance or a mixture?
if the description of the substance and the outcome of the experiment isnt enough to decide, choose \cant decide.\
pure substance
mixture
(cant decide)
is sample b made from a pure substance or a mixture?
if the description of the substance and the outcome of the experiment isnt enough to decide, choose \cant decide.\
pure substance
mixture
(cant decide)

Explanation:

Step1: Analyze sample A

A pure substance has a fixed melting - point and boiling - point and uniform composition. Sample A has a density of 0.77 g/mL. But when cooled to 10.0 °C, two separate clear layers form and disappear when warmed back to room temperature. This phase separation indicates it is a mixture as different components in the mixture have different temperature - dependent solubilities or physical states.

Step2: Analyze sample B

Sample B is a solid yellow cube. When put in a pressure chamber and pressure is increased, an orange liquid seeps out and then stops. This change in the substance under pressure suggests that it is composed of different components. A pure substance would not seep out a different - colored liquid under pressure change without a chemical reaction (and no chemical reaction is indicated here), so it is a mixture.

Answer:

Is sample A made from a pure substance or a mixture? mixture
Is sample B made from a pure substance or a mixture? mixture