Refers to tangible substances that can often be seen or felt. The factory's runoff introduced impurities into the riverbed.
Pro Tip 2/3
Measure and Act
Often used to indicate that action is needed to remove the impurities. We need to measure the impurity levels before purifying the water.
Pro Tip 3/3
Purity Contrast
Highlights the difference from a pure state; anything added that is unwanted. Detecting impurities in this chemical solution is critical for the experiment.