Fluids and Viscosity
Chapter One: Viscosity Describes a
Fluid=s Resistance to Flow.
SECTION 7.1: DESCRIBING FLUIDS
Fluid  any form of matter that flows.
 can be a liquid or a gas.
 Examples: water, syrup,
compressed air in tires
Question: Why can you pour sand, but it
is not considered a fluid?
Sand has a definite shape so it cannot
Aflow@. The sand will not take the
shape of the container.
Fluid Examples
Food
Fluids
Cleanin Body
g Fluids Fluids
Industrial
Fluids
-syrup
- honey
molasses
- water
- oil
- shampoo - blood
- liquid
- mucus
soap
- saliva
- hair gel
- Vim
- motor oil
- compressed
air in tires
States of Matter
SOLIDS LIQUIDS GASES
SHAPE
definite
shape
no
definite
shape
no
definite
shape
VOLUME
definite
volume
definite
volume
no
definite
volume
PARTICLE
ARRANGE
MENT
PARTICLE
MOVEMEN
T
particles particles particles
are close are close are
distant
particles free
random
only
flowing movem
vibrate
ent
Note: Since solids and liquids both have a
definite shape, they are able to flow, so by
definition they are fluids.
Changes of State
FROM /
TO
SOLID
SOLID
LIQUID
GAS
----------
Melting
Sublimation
LIQUID
Solidification
----------
Evaporation
GAS
Deposition
Condensatio
n
----------
Particle Theory Of Matter
1. All matter is made up of tiny particles
2. All the particles in a substance are the
same; different substances are made up of
different particles.
3. There are attractive forces among
particles - these attractions may be weak or
strong.
4. These particles are always moving;
the more energy the particles gain, the
faster they move.
5. There are spaces among the particles.
Worksheet #1: Describe what happens to
water particles as water changes from
solid ice to liquid water to vapor gas. Fill
in the blanks
SECTION 7.2 VISCOSITY AND FLOW
RATE
Viscosity  the measure of a liquid=s
resistance to flow.
 it=s the Athickness@ or
Athinness@ of a fluid. (How runny a fluid
is).
 describes how easily a
fluid flows.
Friction  the rubbing of one object
against another. A force that resists
movement.
Viscosity and Friction
 the more the friction, the higher the
viscosity. Said to be Aviscous@
 determined by the size, shape, and
attraction of the particles of the substance
Viscosity of Products
(1) Must be easy to use
(2) Must fulfill the need
(3) Food and personal care products must
have tactile / sensually pleasing texture
and consistency
Everyday Examples
Many substances require the proper
degree of viscosity to perform their
intended function.
Most times money is a factor associated
with quality in any product. A good ice
cream is creamy and melts in your mouth,
but a cheap ice cream will be chunky and
icy. Pancake batter must be of the right
consistency or they would not form
yummy pancakes. Too solid or runny
would ruin pancake day!!!!!
High Viscosity Examples
Hand cream  rich (viscous) to
be creamy but not gummy and
gross
Wood Glue  must adhere to
surface
Cough Medicine  must cling
to throat, but not choke you
Shampoo  must cling to hair,
but at the same time rinse easily
Paints  require right
viscosity in order to spread
properly
Low Viscosity Examples
Motor Oil  lubricate parts easy to apply
Mouth Wash  must swirl
around in mouth
Hand Soap  must be runny in
order to be pumped out of bottle
Flow Rate  the speed at which a fluid
flows from one point to another.
 often used in
comparing viscosity. (viscosity is hard to
measure)
 liquids flow at different
rates. Water (fast), dishwashing liquid
(medium), and pancake syrup (slow)
 Peanut butter kept in
the fridge is often too viscous to spread.
So......High Flow Rate = Low
Viscosity
Low Flow Rate = High
Viscosity
Core Lab: Flow Rate of Liquids
Question: What others ways could you
determine the viscosity of liquids, besides
the lab?
(Answer: syringe with
constant pressure, splatter test, measure a
circular spread test)
7.3: FACTORS AFFECTING VISCOSITY
The factors listed below have a bigger
impact on liquids than on gasses because
of the spaces between the particles.
(1) Temperature
 A liquid=s viscosity decreases as
the fluid is heated
 A liquids viscosity increases as
the fluid is cooled.
 A gases=s viscosity increases as
the gas is heated
 A gases=s viscosity decreases as
the fluid is cooled.
As heat is added to a liquid the particles
have more energy and pull away from
neighboring particles and slide past them
more easily. This increases the liquid=s
ability to flow, so we can state that its
viscosity is lower.
If heat is taken away from a liquid, the
particles lose energy and move slower.
Because they have less energy, it is harder
for the particles to pull away from other
nearby particles. The liquid loses some of
its ability to flow and its viscosity
becomes higher.
The particle theory states that the particles
in gases are already very far apart. When
energy is added, gas particles speed up
and collide with each other more often,
causing an increase in internal friction,
and therefore an increase in viscosity.
Cooler temperatures in gases keep the
internal friction of particles (and the
viscosity) low.
(2) Concentration
 the amount of a substance
dissolved in a specific volume.
 generally, by increasing the
concentration of a substance, the viscosity
is also increased.
 Example; purity syrup or 2% milk
vs skim milk
(3) Attractive Forces Between Particles
 Attractive forces among particles
of a substance have a major effect on the
viscosity of the substance
 If the attractive forces between
particles are strong, it=s difficult for the
particles to pull away from each other, so
the liquid flows slowly, and therefore has
a high viscosity.
 If the attractive forces among the
particles are weak, the particles pull apart
easily, and the liquid flows easily, so the
viscosity is low.
(4) Particle Size and Shape
 Fluids that are made of small
particles can flow faster (have a low
viscosity) because their particles are able
to move more easily and quickly.
 Some particles in certain fluids
are bigger than others. This means that the
fluid they make up flows much slower
(has a higher viscosity)
 the shape of particles also affects
their ability to slide past one another.