Download Density?

Air Pressure 7.2
Density and Pressure of Air
The air is made up
of molecules.
• Properties • Air has mass.
of Air
Eureka
Density
Density
Density 2
• Since air has mass, it
has other properties,
including density and
pressure.
Density
• Density
• Amount of mass
in a given volume
Density = 5 circles
per cube
Density
• Density
• Amount of mass
in a given volume
Density = 11 circles
per cube
Temperature Affects
Density
2 circles
Density = 6
per cube
Temperature Affects
Density
10circles
circles
Density = 3
per cube
Which rises and which
sinks?
Density =
5 circles
per balloon
Density =
2 circles
per balloon
• Density
Eureka
Density
Density
Density 2
If the molecules are real close the density
is higher.
If the molecules are spread further apart
the density is lower.
Density
Which is Denser?
Which cookie has more
chocolate chips?
A
B
If I wanted to make a cookie less dense
Cookieuse
A is
denser
It has more
I would
the
same. amount
of
chocolate
chips
in the
same
chocolate
chips
just
make
the size
cookie
cookie than cookie B.
bigger.
Which is state of water is
least dense? Most dense?
Solid
Molecules
move very
slowly! They
are close
together.
Most Dense
liquid
Gas
Molecules
move faster
and are more
spread apart.
Molecules
move very
fast! They are
very spread
apart.
Least Dense
Air and Density Clip
Density of
warm and
cold air.
Warm Air
Less Dense
Molecules are
further apart.
Air is lighter.
Cold Air
more Dense
Molecules are
closer
together.
Air is heavier.
Pair/ Share
Temperature
Cold
Air
Temperature
Warm
Air
moreDensity?
Dense
LessDensity?
Dense
Molecules are
Molecular spacing?
closer together.
Air isWeight?
heavier.
Molecules are
Molecular
spacing?
further apart.
Air isWeight?
lighter.
Why do
convection
current
occur?
•Convection currents
happen because hot
air rises. It rises
because it is less
dense and lighter.
•Cold air sinks
because it is more
dense and heavier.
Pair/Share
• Explain how a
convection current
works.
• Use words like: density,
temperature, molecules,
weight
Air Pressure and
Altitude
Less
Dense
Most
Dense
Gravity pulls the
air molecules
toward the earth,
giving them
weight. The
weight of the air
molecules all
around us is called
the air pressure.
18
Atmospheric
Pressure
• The pressure acting
on the surface of the
earth is called
atmospheric pressure.
• It is caused by the
weight of a column of
air pressing down on
the surface of Earth.
• Atmospheric pressure
is measured by a
barometer.
Air pressure
is equal in
all
directions.
20
A Barometer
is
used
to
measure
air
pressure.
21
MILLIBARS
An aneroid barometer uses a cell which has had
most of the air removed.
As the air pressure around the cell increases, it
presses on the cell, which causes the needle to
move.
Barometer Clip
ALTITUDE AND AIR
PRESSURE
• The lower we travel
down into the
atmosphere the more
weight there is
above, and so the
tighter the air is
squished or
compacted.
• Low altitude = high
So why is it harder to air pressure
breath at higher
• High altitude = low
altitudes?
air pressure
Altitude vs Air
pressure Clip
Since pressure changes with altitude…
…how does changing altitude
affect a barometer?
As
elevation
goes up
Barometric
pressure
goes down.
This is an inverse
relationship.
25
Can you feel air pressure?
When you take off or land in an
aircraft, your ears may hurt or feel
uncomfortable. This is because
your eardrums can feel changes in
air pressure as the aircraft moves
quickly up and down.
Astronauts wear space suits so
the can pressurize themselves
in the space suit. With out a
space suit an astronaut would
explode. More inside body
pressure than outside pressure.
Submarines have to be made
very strong to withstand the
enormous pressure exerted by
the water. If they go too low in
altitude they will implode.
9 min video on Air pressure
Most aneroid
barometers have
a needle which
can be set to
remember the
previous reading.
Why would this
be important?
29
Changing Pressure
A rising barometer = increasing air pressure.
This usually means:
30
Changing Pressure
A falling barometer = decreasing air pressure.
This usually means:
Where’d
the
hula
dancer
go?
31
Why do baseball players
like to play in Denver,
Colorado?
• Heat wind and pressure clip