What is viscosity?

• A. Volume
• B. Speed of evaporation
• C. Thickness; measure of resistance to flow
• D. Color of the liquid

Answer: (C)

Viscosity is the thickness of a liquid and its resistance to flow. It describes how much internal friction occurs as layers of the liquid slide past one another. A high-viscosity liquid, like honey, resists motion and flows slowly, while a low-viscosity liquid, like water, flows readily because its molecules slide past more easily. Temperature matters a lot: heating often lowers viscosity by weakening intermolecular forces and increasing molecular motion. In forensics, understanding viscosity helps identify substances (such as different oils or fuels) and predict how they behave at a scene or in a sample. This property is about flow resistance, not how much liquid you have (volume), how fast it dries away (evaporation rate), or what color it appears.