Unit A: Mix and Flow of Matter
Topic 4: Flow Rate and Viscosity
Viscosity: the property that describes a liquid's thickness or
thinness
- Viscous: a thicker liquid
Viscosity
is a property of all fluids (liquids and gases)
·
·
· Some liquids can flow faster than other liquids.
· From what you know, rank the following list of liquids from
fastest flowing (1) to slowest flowing (4):
Water _____
Honey _____
Vegetable Oil ______
Molasses ______
Flow Rate: the time it takes for a fluid to flow from one point
to another point.
Investigation 1F: Determining Flow Rate page 41-43
Question: How fast can different liquids flow?
Product
ProductPerformance
Performanceand
andViscosity
Viscosity
Why might it be important to determine the flow rate and
·· Why
might it be important to know how to determine the flow
rate and viscosity of viscosity
a liquid? of a liquid?
Viscosity
is
an
important
property that
mustthat
be measured
· · Viscosity of liquids is an important
property
must be very
precisely
in
some
industries
measured precisely in some industries
Ex. Manufacturing lipstick Figure 1.22 page 45
· The cosmetics industry depends on flow rate and viscosity
of cosmetics
such aspage
mascara,
lipstick, and nail
Ex. Lipstick
manufacturing
45
· The viscosity
polish depends on the amount of solvent added.
· Solvents keep the ingredients dissolved and fluid while
applying, then evaporate to leave a dry, solid finish
· People in many occupations need to know how to adjust the
viscosity of a substance to suit needs (ex. chefs, mechanics,
artists, technicians, etc.)
Product Appeal and Viscosity
· People in many occupations need to know how to adjust the
viscosity of a substance to suit needs (ex. chefs, mechanics,
artists, technicians, etc.)
· Food manufacturers need to ensure that their foods are the
right consistency (thickness) for their consumers
· They must also know to regulate the effect of heat on the
viscosity of a substance
How Does the Viscosity of Liquids Vary?
Liquids flow at different rates because they have different
viscosities
- Particles can move around, but it might be difficult for them to
pass each other (resistance to flow)
- This creates internal friction
- It is easier for some fluid particles to move past each other than
other fluid particles
- Attractive forces between some particles are stronger than
others
- As the temperature of a substance increases, the
attractive forces of the between the particles
decrease. As the temperature of a substance
decreases, the attractive forces between particles
increases.
- Warmer liquids flow more quickly and cooler liquids
flow more slowly
The viscosity of a liquid DECREASES as
it is HEATED, and INCREASES as it is
COOLED.
How does the viscosity of gases vary?
- Gas particles flow differently than liquid particles
- Gas particles are far apart, so the attractive forces are
low, and the type of gas particle isn't as important
- Gas particles collide rather than slide past each other
- If gas particles are moving in the same direction, viscosity
will be low, BUT as they gain energy and move faster,
gas particles will collide more and viscosity will be high
Ex. Balloon releasing gas
- The temperature of a gas directly affects viscosity
The viscosity of a gas INCREASES as it
is HEATED, and DECREASES as it is
COOLED
(this is the opposite of liquids)
Why?
Topic 4 Review page 49
# 1-6