Download Chapter 15 Study Guide

Chapter 15 Study Guide
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Text pages 430 - 445
15.1 Atmospheric Pressure and Influences
Pressure is defined as the force
a Pascal
(Pa).
exerted on a given area. The unit of pressure is
Here are three examples of pressure which you may have experienced:
1. Air pressure in a bicycle or car tire, often measured in psi (pounds per square
inch)
2. Weather forecasts, air pressure is reported in kilopascals (1 kPa = 1000 Pa)
3. Lower air pressure at higher altitudes when going up a mountain at Whistler
or flying in a plane. Your ears ‘pop’ to equalize the air pressure inside and
outside your ear.
Atmospheric pressure, or air pressure, is the weight per unit area of the gas
particles in the atmosphere due to gravity
. At sea level, atmospheric pressure
averages 101.3 kPa .
A barometer
is an instrument that measures air pressure.
Atmospheric Can Crusher Demo
A pop can has very little water put in it and is then brought to a boil. It is quickly
inverted into a beaker of cold water.
Describe what happens when the pop can makes contact with the cold water.
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What happens to the energy of the air molecules inside the can once you remove it
from the Bunsen burner? How does contact with the cold water affect their energy?
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Thermal Expansion and Air Pressure
According to the kinetic molecular theory
, molecules speed up and spread out
when heated. This creates a region of lower
density, and lower
pressure.
Density and pressure differences explain why hot air rises
and cold air sinks .
The sun heats
the air near
the Earth’s surface.
The heated air expands and
becomes less
dense. It
then floats up through the
surrounding cooler, denser air.
Water vapour mixes with other
gases in the atmosphere. As
warm air rises
, it cools
and some water vapour may
condense into clouds. Further
condensation forms liquid water
droplets and rains
.
A low-pressure cell
is an area of lower air pressure at the Earth’s surface
formed by a warmed air mass that is expanding and rising.
A high-pressure cell
is a region of high pressure at the Earth’s surface formed
by the sinking of denser air.
Isobars are lines of equal atmospheric pressure
often shown on weather maps.
Uneven surface heating also produces convection currents and winds
Weather occurs in the troposphere
troposphere, temperature decreases
.
, the lowest layer of the atmosphere. In the
with height. Combining the amount of
moisture in the air with our knowledge of the movement of high and low pressure
systems, we can predict precipitation.
15.2 Energy Distribution
The Earth is warmer
concentrated in a smaller area
at the equator because the energy of the sun’s rays is
. The Earth is colder
because the energy of the sun’s rays is spread over a larger area
The reason for the seasons is the tilt of the Earth’s axis
strike an area in the summer than in the winter.
at the poles
.
. More rays
Sea and Land breeze
Water has a higher heat capacity
than sand. This means that water heats up
more slowly and it stays warm longer. The resultant pressure difference then
produces winds or breezes.
A) Sea breeze (day)
Air over the land heats up faster
.
It expands, rises and creates a low pressure zone.
The cooler denser air over the water
blows over the land.
The reverse happens during the night.
B) Land breeze (night)
Air over the land cools faster .
It becomes denser and creates a high pressure zone.
The dense air over the land replaces the
less dense air over the water.
A tornado
is a rapidly rotating wind that forms within a thunderstorm. It
forms when hot humid air is covered above by cool dry air. Most tornadoes are 100
to 600 m in diameter, with wind speeds of 125 to 400 km/h. Tornadoes typical last
only a few minutes but can travel several kilometers.
15.3 Global Patterns of Wind and Water
Prevailing Winds are winds that blow in a consistent pattern over large portions of
of the Earth’s surface by the
the globe. They are caused by uneven heating
sun
. This creates two large-scale convection currents at the equator, called
Hadley cells
. The Earth’s rotation does NOT create winds, but it does affect
their direction.
Jet Streams are narrow bands of high-speed westerly winds that occur near the top of
the troposphere.
The Coriolis Effect explains the why the Earth’s rotation
trajectory of an object to appear deflected
.
See http://www.youtube.com/watch?v=mcPs_OdQOYU
causes the
Ocean currents are also created from prevailing winds. Like blowing on the surface
water in a glass, friction between the winds and the ocean produces surface flows.
Ocean currents can transport thermal energy
from the equator to the poles.
The currents affect the temperature of the air blowing above them, which influences
weather such as tropical storms and El Nino
.