Transcript Fluids - 72thompsonlawfield

Unit 2- Fluids
1. Fluids are an important component of many systems.
2. Fluids have different properties that determine how they can
be used.
3. Fluids are essential to life.
1. analyse how the properties of fluids are used in various
technologies, and assess the impact of these technologies on
society and the environment;
2. investigate the properties of fluids;
3. demonstrate an understanding of the properties and uses of
fluids.
• If you had to come up with a definition of “a fluid”, what would
it be?
• Fluids are materials that have no fixed shape and that are
free-flowing (take the shape of their container)
• BOTH liquids and gases are fluids
• How does the scientific definition change your idea of what
fluids are?
• The majority of your body is made up of fluids
• We have all been hearing for years that we are mostly made
up of water (% differs depending on who you talk to)
• Other than water, what other fluids do we have in our bodies?
Fluid
Job within the body
Oxygen
Helps us use the energy within our bodies
Blood
Moves particles into and out of cells
sweat
Cools us down
Saliva
Breaks down our food, helps us swallow
Urine
Takes wastes from body
Stomach acids
Breaks down food for digestion
• Our body has several systems within that help us function every
day. Fluids are integral to several of these systems:
• 1. Circulatory System
• 2. Respiratory System
• 3 .Urinary System
• Moves blood through our body
• Blood carries oxygen, co2,
nutrients, hormones, etc.
• Works with the respiratory
system to create the
cardiovascular system
• The heart pumps to send blood
away from the heart to the
body through arteries (with
oxygen in it) and to the lungs
(to receive oxygen)
• Veins return “used” blood to the
heart to start the process again
• The system that brings air into our bodies
• We take in air, use oxygen, and breathe
out (mostly) carbon dioxide
• Once the air is in our bodies, the
respiratory system works with the
circulatory system to get the oxygen to our
cells
• We inhale through our nose/mouth, the air
travels down the trachea (windpipe), into
the bronchial tubes and into the lungs
• At the end of the bronchioles there are
tiny sacs called alveoli, which absorb the
oxygen into your blood (then the
circulatory system takes over)
• Our bodies produce carbon dioxide as
waste which travels through the
respiratory system in the opposite order
• The diaphragm helps in breathing by
contracting/pulling down during inhalation
and relaxing during exhalation
• Also known as the renal
system, this system rids the
body of waste, regulates
blood pressure, chemicals in
the blood, etc.
• The kidneys filter waste from
the blood and create urine
• If your kidneys don’t filter
waste from the blood
properly, a dialysis machine
can clean your blood for you
• The bladder then stores the
urine until it is ready to exit
the body
1. Is air a fluid? Explain why or why not.
2. Name three fluids that you need in order to live.
3. What do kidneys do? What treatment is needed if kidney’s
don’t work properly?
4. Choose a body fluid. Why is that fluid important to your
body? What do you think would happen to your body without
that fluid?
• Last class, we learned a definition for fluids. Who remembers
what it is?
• Fluids are materials that have no fixed shape and that are
free-flowing
• Liquids and gases are both fluids, but that does not mean they
are the same.
• Each state has its own set of properties- some that are shared
amongst both liquids and gases, some that are different
between the two
• As we discussed earlier, neither liquids or gases have a definite
shape; both take the shape of the container they are in.
Even though you cannot see the gas inside these containers,
the have taken their container’s shape like the liquids- trust
me 
• Liquids have a definite
volume
• If you have 2 L of water, it
doesn’t matter what
container you put it in, the
volume will be 2 L
• if you took the 2 L of coke
in the bottle, and poured it
into the 50 L garbage can,
it would barely cover the
bottom, but there will still
be 2 L of coke
• Gases do not
have a definite
volume
• Think about perfume- If
you spray a tiny bit from a
bottle (a liquid), it
evaporates, becomes a
gas, and fills the whole
room
• All gases will fill whatever
container (or room) they
occupy
• The particle theory helps
explain the similarities and
differences between states
of matter (solids, liquids, and
gases)
Particle theory of matter
1. All matter is made of
particles
2. All particles have empty
spaces between them
3. Particles are constantly
moving in random
directions
4. Particles move faster and
spread further apart when
they are heated
5. Particles are attracted to
one another
• Particles in solids have a
strong connection to one
another and have less
space between them. So,
when they move, they
only vibrate. They do
not slide past one
another which is why
solids have a definite
shape AND volume (and
why solids are not fluids
• In liquids, the particles are
not as strongly attracted.
Therefore, there is more
space between them.
• The connection is strong
enough to hold liquids
together, so they have a
definite volume
• BUT the connection is weak
enough to allow the particles
to slide around more freely,
which is why liquids do not
have a definite shape
• In gases, particles are
really far apart because
they have a weak force
of attraction
• Gas particles go
wherever they please
(within their containers)
which is why they do not
have a definite shape or
volume
• Fill out the chart below to show the differences between solids,
liquids and gases
Attraction
between
particles
Solid
Liquid
Gas
Definite
shape?
Definite
volume?
• All fluids have the ability to flow
• This is a characteristic of fluids
• This happens because the particles inside liquids and gases are
not strongly attracted to one another to stay put; they can move
around (think about what happens when you like a boy or girl.
If you really like them, you stay put. But, if your attraction
fades, you might start to wonder other places)
• Where does oil flow?
• Where does air flow?
• Where does water flow?
• If you fill a container full of sand, poke a hole in the top, and
tip it over, the sand will “flow”, right?
• Does that mean that sand is a fluid?
• The sand isn’t actually flowing
• All the individual grains of sand are moving through the hole
(thanks to gravity) but each gain is keeping it’s shape
• Air, water, and oil particles can flow freely
1. Laminar
• Smooth and regular
• “uninterrupted”
• Less energy required
• 2. Turbulent
• Choppy and irregular
• Something interrupts
• Requires more energy
and moves slower
• The water flow shown
here is an example of
turbulent flow
• What has interrupted the
flow of this water?
• Is this good or bad?
• Turbulent flow of water
is actually great for the
environment!
• It adds oxygen to the
water that living things
need to survive
• Its also a lot of fun for
white water rafters and
kayakers
• Do we want laminar or
turbulent flow of blood
in our circulatory system?
• Why?
• Free-flowing blood is
definitely needed in our
veins and arteries to get
our blood where it needs
to go quickly
• If plaque builds up in our
arteries, it can lead to
blockages that create
turbulence and can cause
blood clots, heart
attacks, and strokes!
• Golf balls have tiny
dimples on them that are
designed to create
turbulent flow of air.
• Why?
1.
2.
3.
4.
5.
6.
What are the two main characteristics of fluids?
What are the 5 parts of the particle theory of matter?
Why can’t solids flow?
Why isn’t salt considered a fluid?
What are the two types of flow? (with examples)
Why are airplane wings designed for laminar flow, not
turbulent flow?
• Some fluids flow very quickly while other flow slowly.
• Give an example of each………
• Molasses flows very
slowly
• Water flows quite
quickly
Why don’t they both flow the same?
• We can determine how fast (or slow) fluids move by measuring the
volume that a fluid moves past a point in a certain amount of time
(like a racer crossing the finish line)
• For example, if it takes you 10 seconds to fill up your 5 L Brita
container from the tap, the flow rate is :
5 L/ 10 s = 0.5 L/s
If you turn your tap on full blast, it will fill faster
Than if you decrease your water flow
**What else might affect flow rate?
•
•
•
•
•
The size of the opening
The force pushing on the fluid
The surface the fluid is flowing over
The type of fluid
Viscosity
•
•
•
•
The substance’s viscosity also affects flow rate
Viscosity is the substances thickness or resistance to flow
Generally, the thicker the fluid, the slower it flows
Think about table syrup- does it flow faster when you leave it
on the counter or keep it in the fridge? Why?
• 1. Cohesion
• 2. Adhesion
• How strongly the particles
in the fluid are attracted to
one another
• The stronger the attraction,
the slower the flow
• Weaker attraction = faster
flow
• How strongly the particles
are attracted to the
particles of another
substance (often the
particles of the container)
• This is why rivers flow more
quickly in the middle than
at the edges
• The viscosity of magma can
affect the type of volcanic
eruption that happens and
even how the volcano is
formed
• Magma that is less viscous
(flows faster) leads to more
eruptions because gas can
escape through it easier
• These types of eruptions are
less violent and lead to lava
flows that create gentle
sloping sides to volcanos
• More viscous (slower flowing)
magma leads to less
eruptions because gas is
trapped
• However, when the
explosions happen, they are
more violent because of the
pressure that builds up
• Lava shoots into the sky and
volcanos with steeper slopes
are formed (because the
lava moves faster)
http://www.youtube.com/watch?v=cn0mIj0_4w
s
• Not all fluids act the
same (as I am sure you
have already realized)
• BUT….would you believe
me if I told you that
there are fluids out there
than can stop bullets and
support your weight??
http://www.youtube.com/watch?v=3zoTKXXN http://www.youtube.com/watch?v=bLiNHqwg
QIU
WaQ
1.
2.
3.
4.
5.
It takes Jimmy 5 minutes to fill a 2 L bottle of molasses. Calculate the flow rate of
the molasses in L/min.
What are the 5 factors that affect flow rate?
What are the two factors that affect viscosity?
How does viscosity affect volcano formation?
Name one non-Newtonian fluid and describe how it is different than “regular fluids
6.
Fill out the cart below to show your understanding of cohesion vs. adhesion
Example
Your hands are wet after washing dishes
The yolk and the egg white stick together when
you pour it into a bowl
Motor oil lubricates the parts of the car’s
engine
A paper clip floats on the surface of water
There is chocolate syrup left in the bottom of
your glass
Cohesion or Adhesion?
• Next class, we will test the viscosity of different fluids
• Let’s brainstorm different liquids that you would like to test…..
• Materials needed: cardboard, plastic sheet, spoon, various
liquids…..
• Procedure: We will time how long it takes each liquid to travel
down the cardboard (or plastic sheet) from start to finish
• Fill out the prediction sheet then compare our predictions to our
results Fluid
Projected Rank
Actual rank (time)
• Density is the measure of the amount of matter per unit volume
of a substance
• Every substance has a density that can be calculated/measured
• Think about two completely different substances; We would
need a lot more Styrofoam to make 1 kg than we would need
to make 1 kg of rocks. This is because rocks have a higher
density than Styrofoam.
• The mass of the particles
(how much matter is in a
substance)
• How tightly packed the
particles are
• The more tightly packet
the particles, the more
dense the substance is
• Last lesson, we looked at
the spaces between
particles in each state of
matter
• Because particles in
solids are closest
together, solids are
usually more dense than
liquids, and gases (least
dense)
• Not all fluids (liquids or gases) have
the same density.
• Think about oil and vinegar salad
dressing. The two parts don’t mix
together even when we shake them.
This is (at least partially) because
vinegar is more dense. Oil will settle
on top (because it is less dense)
• To calculate the density of a substance,
you divide an the mass by the volume.
• D = m/v
or
• ρ = m/v (ρ is the Greek letter “rho”)
• The density of solids and liquids are
commonly expressed in g/mL or g/cm³
• Gases; kg/m³
• Why do you think we measure gases
in kg but solids and liquids in g?
Fluid
Density
Density
(NTP) kg/m³ (STP) kg/m³
Oxygen
1.33
1.43
Carbon
Dioxide
1.84
1.97
Air
1.21
1.29
Methane
0.67
0.72
Natural Gas
Helium
0.7
0.17
0.18
Since helium is less dense than air,
balloons filled with helium float
• **Density can be affected
by temperature and
pressure
• Several common
substances have their
density measured at
• NTP (normal temperature
and pressure) 20ºC
• STP (standard temperature
and pressure) 0ºC
Fluid
Density
(kg/m³)
Temperature
Gasoline
737
15ºC
Milk
1020
15ºC
Olive Oil
800
20ºC
Oxygen
1140
-183ºC
Sea Water
1022
25ºC
• Many substances are
liquids under “normal
conditions”(e.g., room
temperature)
• Other substances require
different conditions to
appear in their liquid
state (see Oxygen)
• At room temperature,
(21ºC), Mercury is the
world’s most dense
liquid (13600 kg/m³)
• Also know as
quicksilver, is the only
metal that is liquid at
room temperature
• Water is one of the few
substances that actually
becomes less dense as it
changes from a liquid to
a solid (1.0 kg/L vs.
0.92 kg/L)
• This is why ice floats to
the top of your drink
• A salt lake in the Middle East
(bordering Jordan, Israel,
and Palestine)
• It is one of the world’s saltiest
bodies of water
• Density = 1.24 kg/L
• Regular salt water is approx.
1.03 kg/L
• Approx. density of a human
is 1.01 kg/L
• Since humans are less dense
than the water of the Dead
Sea, you can “float” in it
• file:///C:/DOCUME~1/athompso/LOCALS~1/Temp/phetdensity/density_en.html
• We are now going to
use graduated cylinders,
water, salt, and food
colouring to make this
happen.
• Anyone know how?
• 1. Density- the measure of the amount of
per
of a substance
• 2. The two factors that affect density
• 3. How do you calculate density?
• 4. Why do ice cubes float in a glass of water?
• 5. Complete the “Solve Density Problems” worksheet (p.173174 of text for a copy, if you lost yours)
• Last lesson, we learned all about density (the amount of matter
per unit volume of a substance)
• Density helps determine whether substances sink or float, but it
is not the only factor
• A screw made of steel will easily sink in water but steel boats
that weight thousands of tons (and carry much more weight)
float in water.
• WHY?
• The upward force that a fluid exerts on an object that opposes
the weight of an object
• An object’s buoyancy determines whether it will sink or float
•
•
•
•
1. Weight of the object
2. Fluid displaced by the object
3. shape of the object
4. Density of the object
• When we put anything in a fluid (think water), the fluid is
displaced (or moved)
• Weight of displaced fluid = upward buoyant force
• Objects float when they displace an amount of water that is
greater than (or equal to) its own weight
• Sinking occurs when the amount of water displaced is less than
its own weight
• The shape of an object affects the amount of fluid it displaces
• Think about a diver vs. a belly flopper;
• Divers (good ones, anyway) enter the water by displacing very
little
• The other guy? Not so much
• The screw is tiny and
displaces very little
water
• The buoyant force acting
on the screw is very
small, cannot support the
weight of the screw
• Cargo ships are large
and have a hollow shell
• They displace a great
deal of water
• The buoyant force acting
on the ship is large, so it
supports the weight of
the ship
• It sinks
• It floats
• The density of the fluid is also a factor in buoyancy
• The denser the fluid, the more buoyancy force, the easier
objects float think back to the Dead Sea example)
• Do you think a ship will float more easily in the Atlantic Ocean
or in Lake Ontario? Why?
• Engineers need to
understand buoyancy to
design ships.
• Most ships have a plimsoll
line painted on them to
show how high (or low) the
ship will float in different
water types
• The notches on the left are
freshwater, salt water on
the right
• http://www.planetseed.c
om/files/flash/science/l
ab/liquids/buoy_exp/e
n/buoyancy.html
• Definition of Buoyancy
• 4 factors that affect buoyancy
• “Check your Understanding” questions from page 177 and
“Will it Sink of Will it Float?” activity on page 178
• Pneumatics- systems that
use compressed fluids
(specifically air or other
gases) to work
• Hydraulics- systems that
used compressed fluids
(specifically liquids) to
do work
•
•
•
•
•
•
Air brakes
Some exercise machines
Pressure gauges
Balloons
Air pumps
Air tubes for mail
• Car lifts
• Water pump
• Combustion engine in a
car
• Pump- forces fluids through
the system
• Conductor- carries fluid
through the system
• Valve- keeps fluids moving
in the right direction at the
right time or stops it at the
right time)
• Pressure Gauge- measures
pressure in the system
• Define “compression”
• Explain the difference between Pneumatics and Hydraulics (and
provide examples of each)
• Identify each of the 4 main parts of a fluid system and the job
of each
• THINGS NOT COVERED IN CLASS (USE YOUR BOOKS)
•
•
•
•
Define pressure and give the formula for it (p. 189)
Pascal’s law (p. 191)
The effect of pressure, volume, and temperature on fluids (p. 195)
Valves (2 examples where they help systems- circulatory system and
engines)- (p. 200-202)