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Viscosity

Definition

Viscosity is a measure of a fluid's resistance to flow.

Do not confuse the term viscous with vicious (mean and nasty!).

Additional Info

Liquids such as molasses or motor oil are examples of highly viscous substances. The viscosity of a liquid generally decreases as the temperature is increased. For example, warm molasses is easier to pour and stir than cold molasses because it has a lower viscosity when warm. Two common units of viscosity are the poise which is 1 dyne per second per square centimeter and the centipoise (100 centipoise = 1 poise). These can also be expressed as (Newton)(second) per square meter. Gases also have a resistance to flow, although these viscosities are much lower than for liquids. When selecting a stirring motor for use with viscous liquids, one generally needs to purchase a unit that has a geared motor that provides the necessary torque. Safety Emporium has a handy selection chart on its lab stirrers page.

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MSDS Relevance

MSDS's are required to list known physical properties such as viscosity (if known and/or relevant). Viscous materials pour slowly and may be difficult to stir. In general, the viscosity of a syrupy material tends to decrease as the temperature increases.

Further Reading

• Info on Viscosity at Hawai'i Space Grant College.
• Viscosity, a well-rounded discussion at Transtronics.
• Viscosity, an entry in the Physics Hypertextbook.
• Viscosity Conversion Factors at Cole-Parmer.
• Gas Viscosity Calculator at LMNO Engineering (enable Java to use).

See also: area units.

Additional definitions from Google and OneLook.

Disclaimer: The information contained herein is believed to be true and accurate, however ILPI makes no guarantees concerning the veracity of any statement. Use of any information on this page is at the reader's own risk. ILPI strongly encourages the reader to consult the appropriate local, state and federal agencies concerning the matters discussed herein.