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 g of a coarse grey powder with a faint unpleasant smell. 15 g of the powder are dissolved in ethanol. 0.5 mg of the resulting black solution is carefully dropped onto a thick sheet of paper laid flat in a tray. After 30 minutes the initial round black stain has spread out and faded in color to a deep purple. Additionally, there is a dark green ring surrounding the inner stain.
• Sample B 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 crystals begin to appear until the liquid is about half crystal, half liquid. After 30 minutes, no more crystals appear, even though the temperature is lowered to 6.3 °C.
Is sample A made from a pure substance or a mixture? If the description of the substance and the outcome of the experiment isn't enough to decide, choose "can't decide.
a. mixture
b. pure substance
c. (can't decide)
Is sample B made from a pure substance or a mixture? If the description of the substance and the outcome of the experiment isn't enough to decide, choose "can't decide."
a. pure substance
b. mixture
c. (can't decide)