Day 1: Fluids Under Pressure KEY QUESTION: How do pressurized fluids affect our lives and the lives of other living things? Looking Ahead • Under pressure, some fluids behave differently than others. • The skills of scientific inquiry can be used to study how fluids are used in hydraulic systems and pneumatic systems. • Fluids are used in systems to accomplish tasks. • Pressurized fluid systems occur in nature as well as in human- made devices. • Technological problem solving skills can be used to create a working model of a hydraulic or pneumatic device. • Human use of fluids technology has social and environmental costs and benefits. CHAPTER 9
Transcript
Day 1: Fluids Under Pressure
KEY QUESTION: How do pressurized fluids affect our lives and the lives of other
living things?
Looking Ahead
• Under pressure, some fluids behave differently than others.
• The skills of scientific inquiry can be used to study how fluids are used in
hydraulic systems and pneumatic systems.
• Fluids are used in systems to accomplish tasks.
• Pressurized fluid systems occur in nature as well as in human-made devices.
• Technological problem solving skills can be used to create a working model of
a hydraulic or pneumatic device.
• Human use of fluids technology has social and environmental costs and
benefits.
CHAPTER
9
Putting the Squeeze on Fluids
• Liquids are much more difficult to compress than gases. Thus
liquids have much less compressibility than gases.
• Pneumatic systems use pressurized gases (often air) to do
work. For example: a pneumatic jack-hammer.
• Hydraulic systems use pressurized liquids (often oil) to do
work. For example: a tractor
• Each hydraulic and pneumatic system have the following
components:
• A pump (to move the fluid)
• Conductors (to carry the fluid)
• Valves (to keep the fluid moving in the
desired direction)
• Pressure gauge (to monitor the pressure)
compress
pneumatic system
hydraulic system
9.1
Fluids Under Pressure — Activity
• Pressurized fluids are used everyday in a variety of things.
• Think of two hydraulic systems, and two pneumatic systems.
• For each system, identify the pump, conductor, and use of the
pressurized fluid.
CHAPTER
9
Chapter 9 – Fluids Under Pressure
Hydraulic System Pump Conductor Use of pressurized liquid
1.
2.
Pneumatic System Pump Conductor Use of pressurized gas
1.
2.
Day 2: Lab Reports for Grade 8 **p.362-363**
• 1. Title
• 2. Testable Question – List questions you are trying
to answer
• 3. Hypothesis – Your prediction
• 4. Equipment List
• 5. Procedure – Point form steps
• 6. Data and Observations – Use a table or graph
• 7. * Analysis and Evaluation – Questions from text
• 8. * Apply & Extend
Conduct an Investigation Investigating Fluids in a Closed System
9.2Pressurized fluids in both hydraulic and pneumatic systems are used to do work. In this activity, you will compare work done by these two types of systems.
Purpose
To compare the effect of using hydraulic and pneumatic systems to move a load.
Equipment and Materials
Today: 1) Complete Investigation
p.230/12) Discuss success criteria
for a LAB REPORT3) Begin report.
Complete LAB REPORT due on Friday at the beginning of class.
• Pressure: The FORCE per unit of area. We use
the unit of Newtons for force
• P = Force/Unit of Area
ex: 1 N/m2
• Pascal (Pa): The unit of measurement for
pressure.
• 1 Pa = 1 N/m2
• Atmospheric Pressure: The force the
atmosphere exerts on a unit of surface area.
• Pascal’s Law: A force applied to a fluid is
distributed evenly through all parts of the fluid.
Day 3: Effects of External Pressure on Fluids Vocabulary
Recall: Pressure is measured in Pascals where:1 Pa = 1 N/m2
9.4• Pressure refers to the force applied to a
unit of surface area.
i.e. pressure (p) = force/unit area
• Atmospheric pressure, or air pressure, is
the force exerted by the atmosphere on a
unit of surface area.
• Atmospheric pressure decreases the
higher you ascend, because there is less
air above you pressing down.
• Pascal’s Law states that a force applied to
a fluid is distributed equally through all
parts of the fluid.
It is this ability of fluids to transfer force
that make them useful in nature and
machines.
CYL
• P.229 #1,2,3
• P.236 #1,2,3,4
PSI – Pounds of force per square inch. One pound per square inchapproximately equals 6894.757
Day 4: Relationships: Pressure, Volume, and Temperature 9.5• When a gas is under pressure (in a closed system), its
volume is decreased.
• Liquids under pressure also have a decreased volume, but it
is so small it is not noticeable.
• The more a gas is compressed into a small volume, the more
collisions that occur between gas particles and the walls of
the container. This means the pressure is greater.
• As temperature increases, the particles of a fluid
move faster and farther apart. This causes the fluid to
increase in volume (expand). If temperature drops, a fluid’s
volume decreases (contracts).
E.g. thermometers.
• Learning Task…
• Use your knowledge of pressure, temperature and
volume to explain how a mercury thermometer works
• Mercury freezes at -39degrees and boils at
357degrees. Use this to explain why it is used in
thermometers.
• Can anyone think of why a propane bottle gets frost
when you use it? Or why windows get frost on the
inside in the winter?
Day 5: The Value of Valves
• Valves are devices that control the movement of a fluid through a
hollow tube or pipe.
• Example: Your circulatory system uses valves:
• Your heart uses valves to pump blood in one direction.
• Your veins use valves to prevent blood from backing up or
pooling.
• Human-built systems also use valves to ensure fluids go in the
desired direction, such as in an internal combustion engine.
valve
internal combustion engine
9.7
The Power of Fluids
• We use pressurized fluids every day
to increase the amount of work we
can do.
• Hydraulic rams are used in
excavators, backhoes, and
front-end loaders because they
can move in and out with
tremendous force and great precision.
• Fire pumps and hoses use hydraulic power to project water or foam
a long distance.
• Hover crafts use pneumatic power to ride on a cushion of air over
land or water.
• Kneeling buses use pneumatic power to make it easier for many
people to access public transportation.
• Some machines use combination systems that use both hydraulic
and pneumatic power, such as with automobile hoists.
9.8
Open your texts…243
Explore an Issue Critically Putting Fluids to Work
9.9The Issue
Select one example of fluid technology and use it to support or refute the state below:
The benefits of using this form of fluid technology outweigh the costs.
Also, identify individual actions that could help alleviate some of the costs, or enhance the benefits, of the technology you have chosen
Communicate
The results of your research and your decisions must be
communicated effectively and concisely in an interesting manner to
your classmates and others in your school. You may choose to
create a poster, brochure, or computer presentation.
Summary – Looking Back
CHAPTER
9• Under pressure, some fluids behave differently than others.
• Pressure is a measure of the force per unit area.
• Gases are more compressible than liquids.
• The particle theory of matter explains the different
behaviour of gases and liquids under pressure.
• There are strong relationships between the
temperature, pressure, and volume of a fluid.
• Systems use fluids to accomplish tasks.
• Hydraulic systems use pressurized liquids to perform tasks.
• Pneumatic systems use pressurized gases to perform tasks.
• Valves allow us to use hydraulic and pneumatic systems in
controlled ways.
Summary – Looking Back
CHAPTER
9• The skills of scientific inquiry can be used to study how fluids
are used in hydraulic systems and pneumatic systems.
• Hydraulic and pneumatic systems can be created using
syringes, tubing, water and air.
• Applications of Pascal’s Law can be modelled using syringes,
tubing, water and air.
• The ability of hydraulic and pneumatic systems to move a load
can be observed using syringes, tubing, water, and air.
• Pressurized fluid systems occur in nature as well as in human-
made devices.
• Atmospheric pressure is exerted by the weight of the
atmosphere.
• Water pressure increases with depth due to the
weight of the water.
• Pressure applied to a fluid is distributed evenly
throughout all parts of the fluid.
Summary – Looking Back
CHAPTER
9• Technological problem solving skills can be used to create a
working model of a hydraulic or pneumatic device.
• Everyday materials and a knowledge of Pascal’s Law can be
used to design, build, and test a working model of an everyday
object that operates using hydraulics or pneumatics.
• Human use of fluids technology has social and environmental
costs and benefits.
• We use pressurized fluids to make our lives more manageable
and to increase the amount of work that humans can do.
• We use pressurized fluids at home, at work, and at play.
• Our use of hydraulic and pneumatic systems allows us to make
major changes to society and the environment.
• Our ability to make such changes must be accompanied by a
commitment to make these choices responsibly.
QuizMultiple choice
For each question, select the best answer from the four alternatives.
1. A system that uses compressed air (or another gas) to do work is called a…
a) Hydraulic system.
b) Low pressure system.
c) Pneumatic system.
d) Open system.
2. What happens when a fluid is under pressure?
a) It contracts.
b) It expands.
c) It cools.
d) Pressure decreases.
3. If a gas exerts 8 N of force over a 2 m2 area, what is the pressure on that area in N/m2?
a) 10.
b) 6.
c) 4.
d) 16.
CHAPTER
9
Quiz
True/False
Indicate whether each of the statements is TRUE or FALSE. If you
think the statement is false, rewrite it to make it true.
4. Liquids are more compressible than gases.
5. Compressing a fluid will decrease its volume.
6. Cooling a fluid will decrease its volume.
7. Valves control the movement of fluid through a tube or pipe.
CHAPTER
9
Quiz
Fill in the blanks
Copy each of the following statements into you notebook. Fill in the
blanks with a word or phrase that correctly completes the sentence.
8. Most fluid systems contain these components: a
to move the fluid; to carry the fluid; to keep
the fluid moving in the desired direction; and a pressure
to monitor the system’s pressure.
9. Your makes use of valves to control the flow of
blood. Valves can be found in your heart and in your
.
10.Machines like backhoes use large syringe-like pistons called
