Foundations of Physical Science Workshop: Viscosity of Fluids

Viscosity of Fluids CPO Science

Key Questions  What is viscosity?  How can viscosity be measured?  How does a molecule’s shape and size affect viscosity?  How does an increase in temperature affect viscosity?

Overview  Define viscosity  Build a viscometer  Measure viscosity of various liquids

What is Viscosity?  A measure of a material’s resistance to flow  Which substance here has a higher viscosity?  How can it be measured?

Viscometer  Uses timer and photogates to measure speed of object moving through a liquid  Indicates the liquid’s resistance to flow

Average Velocity  After setting up Viscometer run three trials using 10 cm for the distance traveled by the marble through the fluid  Use velocity from the three trials to get the average velocity of the marble  Repeat this process for each of the 5 substances

Which Liquid is LEAST Viscous?  Compare average velocities – What will differences in these values indicate about each substance?  What does a high velocity mean?  What does a low velocity mean?  Rank the fluids from least to most viscous

What about Viscosity vs. Density??  Compare the viscosity rankings list with the density ranking list  Is there a relationship?  What do these two terms actually measure?  They seem to be loosely related, but there must be more to the story

Size and viscosity  Which molecule would be easier to pour from a bottle?  Which would experience more friction?  How does that affect viscosity?