Air and Flight---Properties of Air
Air:
- we know it exists,
- it’s all around us,
- we see moving trees,
- it fills our lungs,
- it has substance but can’t be
seen
Air:
- colourless, odourless and
tasteless,
- a gas made mainly of
nitrogen (78%), oxygen (21%)
and small amounts of carbon
dioxide, hydrogen and other
gases
- we can’t taste it, but
- we can feel it.
What do we know about air? What have we
observed?
Air is matter so it must be made up of molecules and atoms. It
interacts with objects because we can see the trees swaying in
the breeze. We also know it moves things since we can see the
clouds moving in the sky and storms approaching us in the
distance. We know that the air must move because it brings us
our weather. Air can change temperature - we can feel the
temperature of the air against our skin. Sometimes air can smell.
It is able to carry the smell of roses to our noses or for that
matter an angry skunk, too. We know that hot air rises and that
hot air can hold more moisture. We see birds using the air to
travel from place to place and we also see seeds being blown
around by the wind. We know that the air can become quite dirty
from dust but also quite polluted. Sometimes we can see the
pollution or smell the pollution. We know that air must take up
space because we have all blown up a balloon or put air in our
bicycle tires.
AIR TAKES UP SPACE
straight
PROPERTIES OF AIR
MATERIALS: -2 glasses ,
-large container to hold water (aquarium, sink)
STEPS
glass1
1-Take two glasses.
2-Place glass#1 straight down into the
water tank.
3-Place the 2nd glass tilted in the water tank
and let it fill up with water. When full, bring
it up and face down and as close to the
surface without removing it from the water.
4- Tilt glass #1 so that you see bubbles
escaping the glass.
5- Try to capture the air bubbles in the
second glass and observe.
WHAT HAPPENED ? (OBSERVATIONS)
glass2
Air
bubbles
Explain what happened to the water in the second glass?
AIR TAKES UP SPACE
PROPERTIES OF AIR
MATERIALS: glasses, large container to
hold water (aquarium, sink), crumpled paper
or washcloth, tape, flexible straws
EXPERIMENT A:
1. Crumple a piece of paper or small washcloth
into the bottom of a
plastic cup (tape may have to be used to keep
the paper at the bottom of the cup).
2. Turn the cup straight over and submerge it
straight under the water.
3. Remove the cup straight out of the water.
WHAT HAPPENED ? (OBSERVATIONS)
Why didn't the paper inside the glass get wet?
EXPERIMENT B:
1. Turn a glass straight over and submerge it straight under the water
2. While under the water tilt the cup slightly to allow some air to
escape and water to rush in. Then place the cup back in a straight
upside-down position.
3. Slip one end of the flexible straw under and inside the glass, while
the other protrudes above the surface of the water.
4. Blow through the straw while your partner holds the glass steady.
WHAT HAPPENED ? (OBSERVATIONS)
straw
Explain what happened to the water in the glass?
glass
AIR RESISTS THINGS MOVING THROUGH ITPROPERTIES OF AIR
crumpled
Steps:
1- Get 2 pieces of paper identical in
weight an size.
2-Crumple one of them.
3-Now, at the same time and from the
same height, drop them.
4-You can see that they don’t hit the
ground first.
intact
Results: (Circle the best answer)
Which one hits the ground first? Why?
A-The paper is heavier after it is crumbled, so it fails to the ground
before the intact paper.
B-The crumpled paper has less area for air to resist and falls the
ground before the intact paper.
C-The crumpled paper has less area for air to resist, and fall to the
ground after the intact paper.
Which events show that air resists things moving through
it? (Circle the best answer)
A- Leaves fall slowly to the ground
B-A book is put on a blown-up balloon.
C- A parachutist jumps from a plane with a parachute.
D-A plastic bag filled with air is poked.
AIR PRESSES ON THINGS-PROPERTIES OF AIR
Materials:
-A glass with smooth rim
-a glossy card(deck of cards)
-water
Procedures:
1-Fill the glass of the rim with water.
2-Place the glossy side of the card down on
the rim of the glass.
3-Keep the palm of your hand on the card and
turn the glass upside down.
4-Take your hand away from the card.
Results:
Explain:
AIR PRESSES ON THINGS-PROPERTIES OF AIR
Materials:
-A glass with smooth rim
-a glossy card(deck of cards)
-water
Procedures:
1-Fill the glass of the rim with water.
2-Place the glossy side of the card down
on the rim of the glass.
3-Keep the palm of your hand on the card and
turn the glass upside down.
4-Take your hand away from the card.
Results:
The card remains attached to the rim of the glass.
The water does not fall out. Why?
Explain:
The air pressure exerted on the card from
underneath is greater than the weight of the water
in the glass. This is why the card can hold the water
in the glass.
AIR EXPANDS WHEN HEATED
PROPERTIES OF AIR
Material:
-Ping pong ball
-Glass
-hot water
Steps:
1-Have a glass of hot water
ready.
2-Put a deformed table tennis
ball in the glass.
Why does this
happen?
Results:
Explain:
Experiment-Properties of Air
Steps:
AIR HAS WEIGHT
1- Inflate two balloons to about the same size and
tie them each with a string.
2-Put a tape on one of the balloons.
3-Tie them each at the end of the rod to make a
scale.
4-Poke a little hole on the tape with a pin.
Results- One end of the scale weighs down.
Explain- Why does this happen?
AIR HAS PRESSURE
PROPERTIES OF AIR
STEPS
1- Lay a ruler on a table so that
about one third of it lies over the
edge.
Material
-ruler -table
-newspaper
2- Spread and smooth a piece of
paper over the ruler.
3-Now try to make the paper fly
into the air by hitting the
ruler downward with a fast and
hard motion.
WHAT HAPPENED ? (OBSERVATIONS)
Explain- Why does this happen?
The student will not be able to lift the paper because air
has weight and is pressing down on it. The surface of
the paper is large, and therefore there is enough force
due to the air pressure on it to prevent it from being
moved by the force applied to the ruler.
Interesting Science Facts
The higher you are in the sky,
the less air there is pressing
down on you. That is why air
pressure is higher at sea level
than at the top of a mountain.
AIR HAS PRESSURE
PROPERTIES OF AIR
STEPS
1- Lay a ruler on a table so that
about one third of it lies over the
edge.
Material
-ruler -table
-newspaper
2- Spread and smooth a piece of
paper over the ruler.
3-Now try to make the paper fly
into the air by hitting the
ruler downward with a fast and
hard motion.
WHAT HAPPENED ? (OBSERVATIONS)
Explain- Why does this happen?
Interesting Science Facts
The higher you are in the sky,
the less air there is pressing
down on you. That is why air
pressure is higher at sea level
than at the top of a mountain.
AIR EXPANDS WHEN HEATED
PROPERTIES OF AIR
Material:
-kettle -ice -bottle
-balloon
STEPS
1. Stretch out a balloon and place its
open end over the mouth of a plastic pop
bottle.
2. The bottle is then submerged in the
hot water container and is observed.
WHAT HAPPENED ? (OBSERVATIONS)
Explain- Why does this happen?
AIR COMPRESSES WHEN COOLED
PROPERTIES OF AIR
3. Next, the bottle is placed into the ice cold water and is
observed.
WHAT HAPPENED ? (OBSERVATIONS)
Explain- Why does this happen?
AIR EXPANDS WHEN HEATED
PROPERTIES OF AIR
Material:
-kettle -ice -bottle
-balloon
STEPS
1. Stretch out a balloon and place its
open end over the mouth of a plastic pop
bottle.
2. The bottle is then submerged in the
hot water container and is observed.
WHAT HAPPENED ? (OBSERVATIONS)
Explain- Why does this happen?
Air expands when heated because the molecules are
further apart. This also has the effect of making warm
air lighter.
AIR COMPRESSES WHEN COOLED
PROPERTIES OF AIR
3. Next, the bottle is placed into the ice cold water and is
observed.
WHAT HAPPENED ? (OBSERVATIONS)
Explain- Why does this happen?
Air compresses when cooled because the molecules
are closer together. This also has the effect of making
cold air heavier.
PROPERTIES OF AIR
Fill in the blanks with the given words.
Two qualities of air enable us to use it as a useful tool.
Air can be 1.______________
and air can act as an 2.________________
Conserve
More
Compressed
Insulator
Air is compressed when more than the regular amount of air has been
pushed into a container. More air in the same space exerts
3-________________ pressure.
Air acts as an insulator when it helps 4-____________
heat. The fur of my dog works in this way by trapping air to keep itself
warm.
Write the letters in the correct boxes.
A
B
Sleeping bag
C
Fire extinguisher
mittens
D
F
E
tire
Compressibility
Spray can
Double paned window
Insulating quality
Match each fact with the property of air.
Write the letter.
Properties of Air
a) Air has weight (mass).
b) Air takes up space.
c) Air presses on things.
d) Air can be compressed.
e) Air resists things moving through it.
f) Air expands when heated.
g) Air has insulating quality.
Air Facts
1. A flat car tire is lighter than when it was full of air.
_____
2. A flat piece of paper falls slower to the ground than a
crumpled piece of paper.
_____
3. Air molecules move around and spread out when heated.
_____
4. Air expands to fill a container, but we may still put more
air in it.
_____
5. A feather down coat traps air within it. It keeps the warmth
in and the cold out.
_____
6. An “empty” water bottle immersed in water upside down
will not fill with water because it is already full of air.
_____
7. A card placed over the rim of a cup of water will hold the
water in place while the cup is upside down. The only thing
holding the card in place is the air underneath the card.
____
FLIGHT
Four Forces of Flight
Before a person can understand flight, they must
first learn about the forces that control flying. A
force is a push or a pull in any direction.
Gravity Force
Gravity is an invisible force which pulls objects together. Objects
with a large mass pull and attract objects with less mass. Because
the earth has a very large mass, all objects near it are pulled
towards the center of the earth. This downwards “pull” Is called
the force of gravity and works against things that are trying to fly.
Drag Force
Drag is a force that slows you down and works in the opposite
direction than you are travelling. For example, when a
parachute on a dragster opens up after the race, it creates a
drag force that helps to slow the car down.
Lift
Lift is a force upward. If the lift force is greater than the gravity
force, the object will stay In the air.
Thrust
This is the force that moves an airplane forward and is usually
produced by a plane’s engines.
forward
What is FORCE?
Floating and Sinking in Fluid Air
By now, you can probably name many materials that are
―natural floaters‖ in water. You also know that materials which
are ―natural sinkers‖ can be made to float. All it takes is a little
reshaping so they hold lots of air.
But a ―natural floater‖ in one fluid may be a ―natural sinker‖ in
another. –This is certainly true for air. The upward buoyant force
that air exerts on objects is usually too small to balance the
downward force of gravity on them. So even an air-filled balloon will
sink in air.
In fact, only a few materials are able to float in air.
One material that floats in air is hotter air!
If you measured equal volumes of hot and cold air on a balance,
you would find that the hot air has less mass than the cold air.
That means hot air can float up through cold air. And that means
it’s possible to help air sinkers become air floaters.
This is what two brothers did in 1783, when they designed, built,
and successfully launched the world’s first hot-air balloon.
The first hot-air balloon was
launched near Paris, France in
1783. It had a mass of more than
600 kg. Even so, the balloon
could hold enough hot air to lift
off and float in the air for 10
minutes before
returning to the ground about I
km away. A huge straw fire was
built under the open end of the
balloon to supply hot air.
Experimenting With a Helium Balloon
Attach paper clips to the string on your helium
balloon to alter the balloon’s mass and density.
Predict and record the number of paper clips
required to float the balloon at different heights
above the ground.
1. Why do helium balloons float in air?
2. How did you control the height at which the balloon
floated?
3. If the air in our classroom was much warmer, would
it change the number of paper clips required to ―sink‖
the helium balloons? Explain.
LIFT vs GRAVITY
Sir Isaac Newton, an English scientist, observed the force of gravity
when he was sitting under a tree and an apple fell on his head! It is a
strong force that pulls everything down toward the earth. The
more mass, the more gravity pulls. The lighter the object the less
lift required to make it buoyant (able to float on air).
Jump up into the air — and stay there! What happens? Do you know of
any place that does not have gravity or much less gravity? Drop a
pencil, rock and a ball. What happens? What does this mean for bigger
and heavier airplanes?
When you lift things up you have to pull against gravity. If you drop a
pencil, gravity pulls it to Earth. If you rest its mid-point on your finger,
gravity will pull down equally on both sides of the pencil and it will
balance in the air.
The attractive force of gravity acts between at the center of two objects.
In the case of people standing on the earth’s surface, the effect of
gravity is to attract us towards the center of the earth. As a result, no
matter where you stand on the earth, you don’t fall off. Gravity is also
the reason why the moon (and satellites) orbit the earth and why we
orbit the sun.
Lift is the upward force
used to overcome gravity
and to achieve flight. Lift
occurs if the force on the
bottom of an object is
greater than the force of
gravity from above. To
sustain a particular height, lift
must equal gravity).
Laws of Flight
1-Bernoulli’s Law of Pressure: The faster air
flows, the less pressure it has.
When air is moving, It creates areas of high pressure and
areas of low pressure. Fast moving air creates an area of
low pressure because the particles are spread further apart
while high pressure air has particles packed closer
together.
2-Law of Flight: Objects always go from high
pressure to low pressure.
A good example of this happens when a hole is made in the
body a passenger plane. The air in the plane is under high
pressure to keep passengers comfortable compared to the low
pressure air outside.
When a hole is made in the body of the plane, objects in the
high pressure plane move violently towards the low pressure air
outside often resulting disasters.
3-Newton’s Third Law: This law says that if there Is a
force in one direction, there is an equal force In the
opposite director.
For example, when a person on a skateboard pushes backwards
on the ground, they move forward. This law helps to explain how
rockets and jet engines work.
WHAT WILL
HAPPEN?
For each of the following:
•Predict what you think will happen
•Perform the experiment
•Draw and describe what you saw happen
Try to explain why this happened
1. Blow over top of a piece of paper
2. Blow under a suspended piece of paper
3. Blow under a folded index card
4. Blow between 2 cups
5. Blow into the bottom of a funnel that has a ping pong ball in it
6. Blow through a straw that is over another straw that is in a cup of
water
7. Hairdryer blowing straight up at a ping pong ball
8. Can you think of a real world example, and/or how
this relates to flight?
The Wing
The picture below shows a side view of a bird’s wing which is
similar to the wing of a glider, airplane or helicopter blade.
1) When air hits the front of the wing (leading edge) it splits up.
2) The air flowing over the curved top of the wing has further to go
than the air going under the flat bottom of the wing.
3) For the two streams of air to reach the back of the wing (trailing
edge) at the same time, the top stream must travel faster than the
bottom. (It has further to go)
4) This fast moving air creates a low pressure area on the top of
the wing and a high pressure area on the bottom of the wing.
(Bernoulli’s Law)
5) Since objects tend to go from high pressure to low pressure, lift
is created, which is how birds and planes stay in the air. (Note that for
the wing to have lift, it must be moving forward through the air)
2. Draw a diagram of how air moves over and under
an airplane wing
3. Why do airplanes take off and land into the
wind?
Bernoulli’s Principle
Draw a labeled diagram of one of the investigations
showing Bernoulli’s Principle.
Describe what happened in this investigation.
Include these words in your explanation:
air
low pressure
stationary
moving
exert
force
high pressure
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