Viscosity: A Property of fluids
307-6 Compare the viscosity of various liquids
307-7 Describe factors that can modify the viscosity of
a liquid
208-6 Design an experiment to test the viscosity of
various common fluids and identify the major variables.
209-7 Demonstrate a knowledge of WHMIS standards
by demonstrating correct methods of disposal of various
oils, for example
109-10, 112-7, 210-12 Identify and relate personal
activities and potential applications to fluid dynamics
What is viscosity?
Viscosity is the term for a liquid’s
thickness or resistance it has when flowing
and moving.
Explain why fluids have different
viscosities?
Different substances are composed of different
particles and have different forces of attraction.
These attractions can be strong or weak.
Explain how the thickness of a fluid
affects its viscosity.
The thicker the fluid is the higher the viscosity.
Ketchup is thick and has a high viscosity.
Maple syrup is not as thick as ketchup and has a
lower viscosity.
If motor oil is not viscous enough (thick), it will not
protect the engine parts from friction;
if it is too viscous, it will not flow to all parts of
the engine that need protection
Salad dressing must be thin enough to pour out of
a bottle, yet thick enough to coat lettuce properly.
Gases are less viscous than liquids, so they
flow very easily through pipes. Ammonia and
carbon dioxide are example of gases moved by
pipeline in Canada
A drinking straw is a means of moving a liquid
from a glass into your mouth, so your mouth acts
as a kind of pump valve.
What force causes the
liquid to move
upwards?
When you suck on a straw, you “vacuum”
the air out of the inside of the straw and
allow the liquid to fill the straw to replace
the missing air.
The pressure acting on the surface of the liquid
helps to push the liquid up into the straw, because
once you “vacuum” out the air, the pressure inside
the straw is lower than outside, and the liquid
moves up easily.
How do you describe Ketchup?
► Thick,
thin
► Slow, fast
► Etc.
What is the difference between
qualitative and quantitative?
Qualitative observations are descriptions
without measurements or numbers.
Such as slow, fast, or quick.
Quantitative are descriptions using
measurements or numbers.
2 liters, 3 feet or 5 centimeters
How can you describe ketchup
quantitatively?
With a viscometer
A viscometer is an instrument used to
measure viscosity
Viscosity is the term for a liquid’s thickness or
resistance it has when flowing and moving.
Changing Viscosity
An increase in temperature represents an increase in
average kinetic energy, and in fluids a decrease in
viscosity. ( Meaning the fluid is not thick but thin
with hot temperatures)
What happens is the particles in the fluid move
faster as the temperature increases. This
weakens the force of attraction between the
particles
The number of particles in the fluid remains
constant regardless of the temperature change.
The force of attraction is what changes.
The heat creates more space between particles
allowing the fluid to flow more freely
Low temperature
High temperature
Understanding Concepts
Molasses has a high viscosity. Explain what this
statement means
In high viscosity fluids, such as molasses, the
resistance to flow is increased. Thus, it is harder
to get molasses to start flowing, and more force
would be requires to keep molasses moving from
one place to another.
How does the thickness of a fluid compare to its
viscosity? Give an example.
Generally, it can be said that a thicker fluid will
have a higher viscosity. The thickness of a fluid
and its viscosity more often correlate than the
density of a fluid and it viscosity
For example, molasses and oil are
thicker and have an increased viscosity
than a thinner liquid like water.
However, the density of some oils, such
as vegetable oil, is less than a thinner
liquid such as water, even though the
viscosity of the oil is greater
Exploring
Research how soap affects the viscosity of water.
Soap actually reduces the viscosity of
water. This allows the water and the soap
to better penetrate the fibres of the
material and clean the fabric.
Inquiry Investigation
Liquids Can Be Thick or Thin
► You
are going to get into groups of 2 and design
an experiment to test the viscosity of at least 5
liquids.
► You should write down exactly what you did each
step of the way.
► Make sure to wear safety goggles while competing
your experiment.
► Then, you will use a water bath and test what
happens to the viscosity of liquids when they are
heated.
► Good luck!
Bell –Aliant Video
► The
Effect of Heat on Matter
► Heating Different Things