Unit Three – Fluids
Chapter Seven: Viscosity Describes a Fluid’s Resistance to Flow.
Chapter 7 Terms
- solid
- fluid
- liquid
- viscosity
- gas
- flow rate
SECTION 7.1 - DESCRIBING FLUIDS (P.268-272)
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 “flow”. The sand will not take the shape of the
container (when sand is in a container there are air pockets between the particles).
Fluid Examples
Food Fluids
- syrup
- honey
- molasses
- water
- oil
Cleaning Fluids
- shampoo
- liquid soap
- hair gel
- Vim
Body Fluids
- blood
- mucus
- saliva
Industrial Fluids
- motor oil
- compressed air in tires
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.
Video - http://www.youtube.com/watch?v=s-KvoVzukHo (states of matter)
States of Matter
SOLIDS
LIQUIDS
GASES
SHAPE
definite shape
no definite shape
no definite shape
VOLUME
definite volume
definite volume
no definite volume
PARTICLE
ARRANGEMENT
particles are very
close
particles are close
particles are
distant
PARTICLE MOVEMENT
particles vibrate in
place
Particles are free
flowing
Particles
demonstrate
random movement
Note: Since liquids and gases both do NOT have a definite shape, they are able to flow,
so by definition they are fluids.
Discuss what happens to the particles of H2O (water) when it changes from a solid to a
liquid to a gas.
Video - http://www.youtube.com/watch?v=2_NLbSbA9xk
Notebook Video
- substance is being _________________
- particles _______________ energy
- ice to water
- _______________ to a _______________
- substance _______________ its definite shape
- substance’s volume stays the same
- the particles of the substance begin to move apart and slide past each
other
- water to steam
- _______________ to a _______________
- substance continues to have NO _______________ shape
- substance’s volume is _______________
- the particles of the substance become _______________ and move
_______________
P. 272 #’s 1, 4, 5
P. 277 #’s 1, 3, 4
SECTION 7.2 - VISCOSITY AND FLOW RATE (P.278-281)
Viscosity
 the measure of a liquid’s resistance to flow.
 it’s the “thickness” or “thinness” 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. It is said to be “viscous”
 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 fluffy pancakes. Too think or
runny would ruin pancake day!
Question: Why is peanut butter kept in the cupboard and margarine in the fridge?
Answer: ______________________________________________________________
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
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 Flow Rate
=
=
Low Viscosity
High Viscosity
Core Lab: The Flow Rate of Liquids (P. 282-283)
Question: What other ways could you determine the viscosity of liquids, besides the lab?
- _______________________________________________________________
- _______________________________________________________________
- _______________________________________________________________
http://www.youtube.com/watch?v=B0QkCWP4HJM&feature=related (cup with hole)
http://www.youtube.com/watch?v=2Hq_jGHiAKk (marbles)
http://www.youtube.com/watch?v=3KU_skfdZVQ (drop rock)
P. 280 #’s 2, 3, 4
P. 281 # 3, 4
P. 285 #’s 7
7.3: FACTORS AFFECTING VISCOSITY (P. 286-288)
The factors listed below have a bigger impact on liquids than on gasses because of the
spaces between the particles.
(1) Temperature
http://www.youtube.com/watch?v=_5te9X4sNrU&feature=related
 A liquid’s viscosity decreases as the fluid is heated.
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.
 A liquid’s viscosity increases as the fluid is cooled.
If heat is taken away from a liquid, the particles lose energy and move slower.
Since 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.
 A gases’s viscosity increases as the gas is heated.
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.
 A gases’s viscosity decreases as the fluid is cooled.
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.
 by increasing the concentration of a substance, the viscosity is also increased.
 Example: whole milk, 2% milk, 1% milk, skim milk
Question: How does the viscosity of Purity Syrup (concentrated) change when you mix it
with water (diluted)?
______________________________________________________________________
______________________________________________________________________
(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.
P. 290 # 5
P. 297 #’s 1, 3, 5,
Chapter Seven foldable
Unit 3 STSE – Soaps and Detergents (one class)
http://animoto.com/play/fTFwfxwToAMKM6XqoMLrHA?utm_content=main_link
Chapter 7 Review Questions P. 298-299 #’s 1, 5, 6, 7, 9, 12, 13